JP2003166115A - Extremely fine fiber, method for producing the same and device for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for extremely simple producing an extremely fine fiber excellent in crystallinity and orientation. <P>SOLUTION: This method for producing the extremely fine fiber is to irradiate a laser beam on a prescribed zone of the fiber while giving ≤1 MPa tension to the fiber which is an almost tensionless state. Thereby, the laser-irradiated part of the fiber is stretched and becomes extremely fine having ≤5 μm diameter. Also, a birefringence of the obtained extremely fine fiber is high, and the fiber is excellent in crystallinity and orientation. Since the extremely fine fiber is obtained by only irradiating the laser beam on the fiber while giving a minute tension on it, the extremely fine fiber can be provided at a low cost. Further, by irradiating the laser beam on the fiber obtained by performing the zone stretching, while giving ≤1 MPa tension, it is possible to obtain a super extremely fine fiber having ≤2 μm diameter. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrafine fiber, a method for drawing the fiber, and a production apparatus for producing the ultrafine fiber. More specifically, it is very easy to produce an ultrafine fiber having high strength and the ultrafine fiber. And a manufacturing apparatus for realizing the method.

[0002]

2. Description of the Related Art With the development of spinning technology for synthetic fibers, 1D
Research and development for producing ultrafine fibers of (denier) (diameter of about 10 μm to 12 μm) or less have been actively conducted.
Ultrafine fibers are used, for example, in artificial suede and wiping cloths, and because of their small fiber diameter, they are also widely used, for example, in air purification, liquid separation, medical filters, etc., in addition to textiles and clothing. .

Direct spinning methods and multi-component spinning methods are known as methods for producing such ultrafine fibers. When producing ultrafine fibers by the direct spinning method, a method of lowering the viscosity and increasing the cooling rate is used. However, the direct spinning method alone has a limit to the ultrafine size, and thus methods such as the multi-component spinning method and the special spinning method have been developed. The multi-component spinning method is a method of producing ultrafine fibers mainly using two components, and is classified into a dissolution type and a separation split type. In the dissolution type, for example, by spinning using a special spinneret, a sea-island in which a large number of minute regions consisting of one component of the two components independently exist Spinning into fibers called mold fibers,
Ultrafine fibers composed of island components are obtained by dissolving sea components.
In the separation-division type, fibers having two components that are adjacent to each other in a radial shape, a hollow ring shape, or a multi-layered parallel shape are separated and separated by mechanical stimulation or chemical treatment to produce ultrafine fibers.

[0004]

In any of the above-mentioned multi-component spinning methods, since high precision is required for the spinneret and the spinning technique, a special apparatus is required and the manufacturing cost is high. Further, there is a problem that the materials to be used are limited because it is necessary to mix or combine the two components. Therefore, a method for easily producing ultrafine fibers at low cost has been desired.

Further, a method of making a fiber fine by drawing is also known, but there is a problem that as the fiber diameter becomes smaller, it becomes easier to break the fiber, and it is virtually impossible to make an ultrafine fiber by the drawing method. Was there.

The present invention has been made to meet such a demand, and a first object of the present invention is to provide a novel manufacturing method capable of easily manufacturing ultrafine fibers at low cost. It is in.

A second object of the present invention is to provide a novel method for producing ultrafine fibers by the drawing method.

A third object of the present invention is to provide ultrafine fibers having high crystallinity and high orientation.

A fourth object of the present invention is to provide a manufacturing apparatus for manufacturing ultrafine fibers having high birefringence at low cost.

[0010]

According to a first aspect of the present invention, there is provided a method for drawing a fiber by irradiating the fiber with laser light while applying a tension of 1 MPa or less.

The inventors of the present invention radiated a laser beam to a fiber to which a minute tension of 1 MPa or less was applied and heat-stretched the fiber. The fiber irradiated with the laser beam was stretched and had a diameter of 5 μm or less. It has been found that ultrafine fibers can be obtained.
The birefringence of the obtained ultrafine fibers was extremely high.
This suggests that not only stretching by flow but also oriented crystallization occurs, and the crystallinity and orientation are high,
This means that high strength fibers are obtained. When the draw ratio was determined from the fiber diameter before and after drawing based on the following formula (1), the draw ratio was 5 to 7 times in the conventional drawing method, whereas in the present invention, the draw ratio is 1000 times or more, which is extremely high. I was able to get the magnification.

Draw ratio λ = (d ₀ / d) ² (1) (where, d ₀ is the diameter of the fibril before stretching, d is the diameter of the fiber after stretching, (Fiber density is constant before and after drawing)

The diameter of the ultrafine fibers obtained by drawing was uniform, and the surface was not deteriorated by laser ablation. As described above, in the production method of the present invention, an extremely high-quality ultrafine fiber excellent in crystallinity and mechanical properties is obtained by an extremely simple method of irradiating with laser light and heating and stretching while applying a minute tension to the fiber. Obtainable. This makes it possible to provide high quality and inexpensive ultrafine fibers. In this specification, a method of irradiating a fiber with a laser beam to heat and draw the fiber is referred to as a “laser heating drawing method”.

In the present invention, the tension applied to the fiber is 1M.
It is not more than Pa, the fibers are not twisted, and the fibers are almost tensionless. The tension applied to the fibers may be such that the fibers extend linearly, more preferably 0.66 MPa.
It is the following. To apply tension to the fiber, it is preferable to support one end (upper end) of the fiber and suspend it vertically and attach a weight to the other end (lower end). You may apply tension.

The fibers to be ultrafine by the manufacturing method of the present invention are preferably synthetic fibers (artificial fibers) such as crystalline polymers such as polyethylene terephthalate, nylon and polypropylene, and amorphous polymers. The present invention can also be applied to natural fibers such as silk.

In the manufacturing method of the present invention, any laser light can be used as the laser light for irradiating the fiber, and for example, a gas laser such as a carbon dioxide gas laser, a fixed laser such as a semiconductor laser, and a liquid such as a dye laser. A laser can be used. The laser light may be pulsed or DC light (CW laser). As the laser wavelength, various wavelengths in the far ultraviolet to infrared region can be selected. It is preferable to adjust the output power and the focusing degree of the laser light so that the laser power density of the laser light irradiation portion of the fiber is 15 W / cm ³ or more. Generally, the higher the laser power density, the finer the fiber can be obtained. all right.

The fiber drawn by the method of the present invention is preferably a fiber previously drawn by hot drawing or zone drawing, and particularly preferably a fiber drawn by zone drawing. Zone drawing is a method of drawing an undrawn fiber, for example, while moving a heating body such as a heater at a constant speed with respect to the fiber. It is preferable to apply laser heating stretching. Ultrafine fibers can be obtained by subjecting the fibers thus zone-drawn to laser heating drawing. Such a method is suitable as a method for making a fiber having a relatively large fiber diameter extremely thin. The zone stretching method is specifically disclosed in Japanese Patent No. 1343924, which can be referred to.

Further, in the manufacturing method of the present invention, the fiber can be irradiated with laser light in a stepwise manner to be drawn.
That is, it is possible to irradiate a fiber under a predetermined tension with laser light at least once to draw the fiber to a predetermined thinness, and then irradiate the fiber with a laser light under a tension of 1 MPa or less to draw. As described above, by irradiating the fiber with the laser light a plurality of times to draw the fiber, an ultrafine fiber can be obtained.

The reason why ultrafine fibers can be obtained by performing the drawing of the fibers by laser light irradiation several times in this way is considered to be based on the following principle. That is, when the fiber drawing by laser light irradiation is performed several times, it is considered that the fiber is crystallized to some extent by the first drawing by laser light irradiation, and the crystallinity of the fiber is enhanced. Here, it is considered that the fiber having high crystallinity (hereinafter referred to as high crystallinity fiber) has a higher melting point than the fiber having low crystallinity (hereinafter referred to as low crystallinity fiber). That is, comparing the temperatures of the high-crystallinity fiber and the low-crystallinity fiber that are melted by laser light irradiation, the temperature of the former is higher than that of the latter. Therefore, since the melted portion of the highly crystalline fiber has a lower viscosity than the melted portion of the low crystalline fiber, the highly crystalline fiber is easier to draw. Therefore, by irradiating the laser light a plurality of times, a finer fiber can be obtained as compared with the case of irradiating the laser light only once. Incidentally, in the fiber irradiated with the laser light a plurality of times, the expansion of the fiber has been confirmed in the portion where the stretching has started, and the reason for this is not clear yet, but it is related to the fiber becoming extremely fine. I think that the. When the ultrafine fibers were obtained by irradiating the laser light only once, the expansion of the fibers was not confirmed in the drawing start portion.

In the manufacturing method of the present invention, it is preferable to move the fiber relatively to the laser beam in order to further increase the draw ratio. The relative moving speed is 300 mm / min to 3000 mm in order to obtain ultrafine fibers.
/ Min is preferable.

According to a second aspect of the present invention there is provided a drawn fiber obtained using the method of the first aspect of the present invention. The stretched fiber is preferably a fiber composed of a thermoplastic polymer, for example, polyethylene terephthalate, polypropylene, nylon 6, nylon 66, polyethylene, polyvinyl alcohol, polyacrylonitrile, polystyrene, polyamide, polychlorinated material. Vinyl, polyoxyethylene, polytetrafluoroethylene, polyether ether ketone,
Fibers such as polymethyl methacrylate and polyethylene 2,6 naphthalate (PEN) can be used, and polyethylene terephthalate, polypropylene and nylon 6 are particularly preferable. Even if such a drawn fiber has an extremely fine thickness of 5 μm or less, it is 25 × 10 ^{−3 to} 120 × 10 ^−3.
Since it has a high birefringence, it is excellent in strength and easy to process.

According to a third aspect of the present invention, nylon 6
The fiber has a diameter of 2 μm or less and a birefringence of 4
Nylon 6 fibers are provided that are in the range of 0 × 10 ⁻³ to 50 × 10 ⁻³ . To the inventor of the present invention, there is no ultrafine nylon 6 fiber having a diameter of 2 μm or less having such high birefringence. Such ultrafine fibers can be manufactured at low cost using the manufacturing method of the present invention, for example.

According to a fourth aspect of the present invention, the polypropylene fiber has a diameter of 2 μm or less and a birefringence in the range of 25 × 10 ^{−3 to} 35 × 10 ^−3. Polypropylene fibers are provided. To the inventors' knowledge, there is no such ultrafine polypropylene fiber having a diameter of 2 μm or less having such a high birefringence. Such ultrafine polypropylene fibers can be manufactured at low cost using the manufacturing method of the present invention, for example.

According to a fifth aspect of the present invention, the polyethylene terephthalate fiber has a diameter of 5 μm or less and a birefringence of 70 × 10 ^{−3 to} 120 × 10 ^−3. Polyethylene terephthalate fibers are provided. To the inventor of the present invention, there is no superfine polyethylene terephthalate fiber having a diameter of 5 μm or less having such a high birefringence. Such ultrafine polyethylene terephthalate fiber can be manufactured at low cost using, for example, the manufacturing method of the present invention.

The ultrafine fibers of the third to fifth aspects of the present invention are
All have higher birefringence than conventional ultrafine fibers. Such ultrafine fibers having a high birefringence generally have excellent strength and thus have an advantage of being easily processed. The reason for the high birefringence in the ultrafine fibers of the present invention is that the molecular chains are selectively oriented in a predetermined direction by applying stress to the polymer chains constituting the fibers by laser heating and drawing, and thus the orientation of crystals. It is thought that this is because both the degree of orientation and the degree of amorphous orientation are increasing. Further, as can be seen from the observation results of wide-angle X-ray diffraction photographs of Examples described later, diffraction spots based on crystals are clearly observed, and thus it is considered that the crystallinity is also high.

The birefringence of a fiber is usually defined as the difference between the refractive index in the direction of the fiber axis and the refractive index in the direction perpendicular to the fiber axis. The birefringence Δn of the crystalline fiber can be generally expressed by the following equation.

[0027] Δn = X_Vf_cΔn_c ⁰+ (1-X) f_aΔn_a ⁰ Where X_VIndicates volume crystallinity, and Δn_c ⁰And Δn_a
⁰Indicate the intrinsic birefringence for the crystalline and amorphous parts, respectively.
And f_cIs the degree of orientation of the crystal part (also called the crystal orientation coefficient)
F_aIndicates the orientation degree of the amorphous part. Intrinsic birefringence
Is the birefringence when the molecular chains that make up the fiber are perfectly oriented.
Occasionally. The result when the crystal parts of the fiber are perfectly oriented
Orientation degree f of crystal part_cIs 1, and the polypropylene of the present invention
For the fibers, the results of wide-angle X-ray diffraction photographs of Examples described later
As a result, the degree of crystal orientation is 0.9 or higher, which is extremely high.
It is considered to be a high value.

The orientation of the fiber can be evaluated from the intrinsic birefringence of the crystal part of the polymer material constituting the fiber. That is, since the intrinsic birefringence is the ultimate birefringence when the molecular chains are completely oriented as described above, the birefringence value of the fiber becomes higher as the value approaches the intrinsic birefringence. You can evaluate it. For example, in the case of nylon 6 fiber, the intrinsic birefringence is about 0.096 at maximum according to various reports. On the other hand, the birefringence of the nylon 6 fiber of the present invention is 0.040 to 0.050,
It can be seen that the nylon 6 fiber of the present invention has high orientation.

Further, the intrinsic birefringence of polypropylene fiber is 0.064 at maximum according to various reported examples. on the other hand,
The birefringence of the polypropylene ultrafine fibers of the present invention is 0.025.
.About.0.035, and the ultrafine polypropylene fiber of the present invention has higher orientation than the conventional polypropylene fiber.

The intrinsic birefringence of PET fiber is about 0.290 at maximum according to various reports. On the other hand, the birefringence of the PET fiber of the present invention is 0.070 to 0.120, and the ultrafine PET fiber of the present invention has higher orientation than before.

According to a sixth aspect of the present invention, there is provided a manufacturing apparatus for manufacturing an ultrafine fiber, which comprises a laser light source for irradiating the fiber with a laser beam, and the fiber for the laser beam. A manufacturing apparatus including a fiber moving device for relative movement is provided.

Since such a manufacturing apparatus can realize the manufacturing method of the first aspect of the present invention, it is possible to easily manufacture ultrafine fibers having high birefringence at low cost.

In the manufacturing apparatus of the present invention, a gas laser light source such as a carbon dioxide gas laser or an Ar gas laser, a semiconductor laser or the like can be used as the laser light source. The laser light source is preferably arranged so that the laser light is emitted perpendicularly to the fiber axis direction. Alternatively, a mirror or the like may be provided so that the laser light from the laser light source is emitted perpendicularly to the axial direction of the fiber. Further, the manufacturing apparatus may include a lens for condensing the laser light emitted from the laser light source on the fiber.

The production apparatus of the present invention can be provided with a supporting portion for supporting one end of the fibril before drawing. Such a supporting portion can be configured, for example, by using a chuck or the like when fixing and supporting the fibrils, and by using a pulley or the like when supporting the fibrils sent from the fiber delivery device described later. You can The support part can support the fibrils so that the fibrils extend in the vertical direction, for example. In this case, the fiber moving device can be configured to include a movable portion connected to the support portion and a guide portion that movably guides the movable portion. As the guide portion, for example, a rack and pinion, a ball screw, a timing belt or a linear motor can be used. By moving the movable portion connected to the support portion in the vertical direction by the guide portion, the fibril supported by the support portion can be moved in the vertical direction.

Further, the production apparatus of the present invention uses 1MP for a fiber.
A holding portion for holding the other end of the fibril can be provided so that a tension of a or less is applied. As the holding portion, for example, a chuck, a fixed pulley, a moving pulley, or the like can be used. When the fibrils are held by the chuck, a weight or the like can be attached to control the tension applied to the fibrils.

In the manufacturing apparatus of the present invention, the fiber moving device includes a fiber delivery device for delivering the raw fiber to be laser-heated and drawn, and an ultrafine fiber delivered from the fiber delivery device and then drawn by laser-heated drawing. And a fiber winding device for winding. The raw fiber delivered from the fiber delivery device is supported by a supporting portion such as a pulley, and then wound by a fiber winding device through a holding portion such as a fixed pulley or a moving pulley. In this case, the relative speed of the fiber to the laser light can be controlled by controlling the speed at which the fiber is delivered by the fiber delivery device and the speed at which the fiber is wound by the fiber winding device.

When the moving pulley is used as the holding portion as described above, a sensor for measuring the height position of the moving pulley can be provided. In this case, it is preferable to control the fiber winding speed of the fiber winding device so that the height position of the moving pulley becomes constant based on the height position of the moving pulley measured by the sensor. By applying the load of the moving pulley itself or a constant load to the moving pulley, it is possible to always give a constant tension to the fiber. In addition, a guide rail for guiding the moving pulley is provided, and even if the winding speed of the fiber is controlled by the fiber winding device so that the position of the moving pulley on the guide rail is constant, the tension of the fiber is kept constant. Can be given.

In the manufacturing apparatus of the present invention, the supporting section can be configured to simultaneously support a plurality of fibers.
In this case, it is preferable to provide a cylindrical lens or a polygon mirror so that the plurality of fibers supported by the supporting unit are respectively irradiated with the laser light from the laser light source.

[0039]

BEST MODE FOR CARRYING OUT THE INVENTION The ultrafine fibers, the manufacturing method and the manufacturing apparatus according to the present invention will be specifically described below with reference to Examples, but the present invention is not limited thereto.

[0040]

First Embodiment First, a manufacturing apparatus according to the present invention will be described. FIG. 5 shows a schematic configuration diagram of the manufacturing apparatus. Device 5
00 is mainly composed of a continuous carbon dioxide laser oscillator 51, a power meter 53, a shutter 54, a fiber moving device 55, and a pair of pulleys 56. The fiber moving device 55 is
Cross head 57 that moves by rack and pinion system
And two guide rails 58 extending in the vertical direction and formed with a spiral screw, and a motor (not shown),
By rotating the guide rail 58 with a motor, the crosshead 57 can slide on the two guide rails 58 at a constant speed. The cross head 57 is provided with a support rod 59 extending in the horizontal direction. Support rod 5
One end of the fibrils is attached to the tip of 9 so that the fibrils can be suspended. A weight 60 having a predetermined weight is attached to the other end of the fibril, and the tension applied to the fiber (hereinafter referred to as applied tension) can be adjusted by changing the weight of the weight 60. Further, the fibrils suspended from the tip of the support rod 59 are linearly aligned by the two pulleys 56 and positioned at a predetermined target position of laser light. By raising or lowering the crosshead 57, the fiber attached to the tip of the support rod 59 is moved relatively at a constant speed with respect to the laser light from the continuous carbon dioxide gas laser oscillator 51.

The continuous carbon dioxide gas laser oscillator 51 is 10.
It has an oscillation wavelength of 6 μm, the maximum output is 10 W, and the beam diameter is 4.3 mm. The power meter 53 has a detector 52. The detector 52 is arranged on the optical path of the laser light when measuring the power of the laser light emitted from the continuous carbon dioxide laser oscillator 51, detects the light intensity of the laser light, and uses a power meter 53 connected to the detector 52 to detect the laser light. The light power is read out.

Further, a shutter 54 is provided on the optical path of the laser light.
Is provided, and by opening and closing the shutter 54, it is possible to control the on / off of laser light irradiation to the fibrils.

[Laser Heating Stretching] Next, the device 5
A method for producing ultrafine fibers by laser-drawing PET fibers using No. 00 will be described.

First, PET fibers were prepared as raw fibers. The PET fiber was produced by melt spinning a pellet (number average molecular weight: about 30,000) manufactured by Kanebo Gosei Co., Ltd. at 270 ° C. using a melt spinning machine (not shown). The prepared fibrils have a diameter of about 130 μm and a birefringence of 0.7 × 10.
^-3 , the crystallinity was 4.5%, and the fiber was a substantially amorphous non-oriented fiber.

Next, the fibrils were mounted on the apparatus shown in FIG. 5, and while the crosshead 57 was lowered at a speed of 500 mm / min, a predetermined portion of the fibrils was irradiated with laser light perpendicularly to the fibrils. . In this case, the laser power density of the fiber portion irradiated with the laser light is 21 W / c.
It was m ² . The laser light irradiation portion of the fibril was instantaneously (millisecond order) stretched by the heating by the laser light irradiation, and the laser light irradiation was stopped simultaneously with the stretching. At this time, it was found that the lower end of the fiber descended at a speed of about 150 m / min. When the laser light irradiation part of the fibril was observed, it was drawn and extra fine.

[Measurement of Diameter and Birefringence] Furthermore, the tension applied to the fibrils and the laser power density of the fibrils at the laser light irradiation portion were changed to various values, and the same laser heating drawing was performed to obtain various ultrafine fibers. Fibers were made. Then, the diameter and birefringence of each ultrafine fiber were measured and SEM observation was performed. The diameter of the ultrafine fibers was measured using a microscope, and the birefringence was measured using a polarizing microscope equipped with a Berek compensator.

In FIG. 1, the laser power densities PD are 11.8 W / cm ² , 14.2 W / cm ² and 15.8 W, respectively.
² shows a graph of the diameter of the ultrafine fibers against the applied tension in the cases of / cm ² and 21.0 W / cm ² . Further, FIG. 2 shows a change in birefringence of the ultrafine fibers with respect to the applied tension in each of the laser power densities PD.

As shown in FIG. 1, the applied tension is 1.6MP.
If it is a or more, the diameter of the ultrafine fiber depends on the laser power density.
Nevertheless, it shows almost constant value. However, the sign
When the tension is 1 MPa or less, the diameter of the ultrafine fibers is small.
The smaller the applied tension, the finer the resulting fiber.
The diameter of the fibers is also small. In particular, applied tension σ_aIs 0.66MP
Laser power density PD is 15.8 W / cm at a or less.^Two
And 21.0 W / cm ^TwoIs relatively high, the diameter is 5μ
Ultrafine fibers of m or less were obtained. Laser power density
PD = 15.8 W / cm^TwoAnd PD = 21.0 W / cm
^TwoIn case of, apply tension of 0.66 to 1.6 MPa
Fiber was cut before it was fully drawn (Fig. 1
(Middle, broken line part).

On the other hand, the birefringence of the ultrafine fibers decreases as the applied tension σa decreases and the laser power density PD increases, as shown in FIG. However, when the laser power density is relatively high at 15.8 W / cm ² and 21.0 W / cm ² , the birefringence of the ultrafine fibers starts to decrease and then increases when the applied tension σa becomes 0.66 MPa or less. , The birefringence is high. That is, the ultrafine fibers show high orientation. From the results shown in FIGS. 1 and 2, the laser power densities were 15.8 W / cm ² and 21.0 W / c.
It can be seen that when the applied tension is relatively high as m ² and the applied tension is 0.66 MPa or less, ultrafine fibers having a diameter of 5 μm or less and having high crystallinity and high orientation are obtained.

The laser power density PD is 21.0W.
/ Cm ² and the applied tension is 0.17 MPa, the fiber is most drawn, the diameter is 4.5 μm, and the birefringence is 0.
It was 112. Assuming that the density of the fiber was constant before and after the stretching, the stretching ratio λ was calculated from the fiber diameter based on the above formula (1), and it was 1060 times, which was a very high value.

The laser power density PD is 21.0W.
Wide-angle X-ray diffraction was performed to investigate the orientation of the ultrafine fibers obtained when the applied tension was 0.17 MPa / cm ² and a slight diffraction spot was observed, similar to the results in FIG. It was confirmed that the microcrystals forming the fiber were oriented.

[Observation with Scanning Electron Microscope (SEM)] FIG. 3A shows the fibrils and σ _a = 0.17 MPa.
The SEM photograph of 350 times each of the ultrafine fibers drawn under the condition of PD = 21.0 W / cm ² is shown in FIG.
(B) shows a SEM photograph of the ultrafine fibers at 10000 times. No laser ablation was observed on the surface of the ultrafine fibers, and the fiber diameter and the fiber surface were uniform. Also, FT-
It was also confirmed from IR (Fourier Transform Infrared Spectrometer) measurement that ablation did not occur.

[Movement speed dependence] Next, the applied tension is
Fix the fiber at 0.17 MPa and transfer the fibrils to the laser light.
The laser speed and laser power density were changed to various values and laser
The heating and drawing are performed, and the moving speed of the fibrils with respect to the laser light
And the relationship between the diameter of the ultrafine fibers obtained by
It was In FIG. 4, the moving speed is 300 mm / min, 600 m
m / min, 900 mm / min and 1800 mm / m
of the change in fiber diameter with laser power at in
A graph is shown. As shown in FIG.
With increasing diameter, the diameter of the obtained fiber decreases,
Laser power density is 10 ~ 60W / cm ^TwoMove within
When the speed is 600 mm / min, the fibers become fine
There is. Laser power density is 55.4 W / cm^TwoAt
The finest fibers (diameter 4.72 μm) were obtained. Well
The birefringence of such ultrafine fibers is 0.107, and
The magnification was 1051 times.

[Change in Diameter and Birefringence of Ultrafine Fiber] Next, laser heating drawing was carried out with an applied tension of 0.17 MPa, a moving speed of the fibril with respect to laser light of 500 mm / min, and a laser power density of 21 W / cm ^2. With respect to the ultrafine fibers obtained by performing the above, the change of the diameter and the birefringence with respect to the distance ΔL from the portion (hereinafter referred to as the neck portion) where the fibril portion began to become thin as shown in FIG. 18 was examined. FIG. 14 shows the distance ΔL from the neck portion of the ultrafine fibers and the diameter and birefringence at the position of the distance ΔL.

As can be seen from FIG. 14, the diameter of the obtained fiber is extremely thinned to 5 μm or less when the distance ΔL from the neck is in the range of 20 mm to 820 mm. On the other hand, the birefringence has a distance ΔL from the neck of 50 mm to 7 mm.
It can be seen that a high value of 70 × 10 ⁻³ or more is shown in the range of 50 mm. Particularly, in the portion near the neck, an extremely high birefringence of 150 × 10 ⁻³ is obtained.

[0056]

Example 2 In this example, an example of applying the laser heating drawing of the present invention to nylon will be described.

An unstretched nylon 6 fiber manufactured by Toray Industries, Inc. was used as the raw fiber. Such fibers have a diameter of 0.189 m.
m, birefringence 6.25 × 10 ⁻³ , crystallinity 27.6%
Met. The fibrils were mounted on the apparatus shown in FIG. 5 in the same manner as in Example 1, and the tension applied to the fibrils and the laser power density were changed to various values, and the fibrils were laser-heated and drawn. In this example, the moving speed of the crosshead of the apparatus shown in FIG. 5, that is, the moving speed of the fibrils with respect to the laser light was set to 300 mm / min. The diameter and birefringence of the various ultrafine fibers thus obtained were measured.

FIGS. 6 (A) and 6 (B) show the fiber diameter and birefringence with respect to the laser power density when laser heating and drawing are performed at various applied tensions and laser power densities, respectively. As can be seen from FIG. 6A, the applied tension σ _a is 0.
Ultrafine fibers were obtained when laser heating and drawing were performed at 18 MPa and 0.37 MPa and the laser power density PD was 25.9 W / cm ² or more. As shown in FIG. 6 (B), as shown in FIG. The refraction is about 30 × 10 ⁻³ .
The finest fibers were obtained when the applied tension σ _a was set to 0.18 MPa and the laser power density PD was set to 69 W / cm ² . The ultrafine fibers had a diameter of 4.7 μm and a birefringence of 29 × 10 ⁻³ . In addition, the draw ratio calculated from the fiber diameter reached 1617 times. FIG. 7 shows an SEM photograph of such ultrafine fibers. Laser ablation was not observed on the surface of the fiber, and the fiber diameter and the fiber surface were uniform.

On the other hand, when the applied tension σ _a was set to 1.1 MPa or more and the laser power density PD was set to 25.9 W / cm ² or more, the fiber was cut and could not be stretched. . Also, the applied tension σ _a is 1.1 M
Laser power density PD of 25.9 W / cm
^When laser heating drawing was performed under the setting of ² or less, ultrafine fibers could not be obtained.

As shown in this example, the nylon 6 fibers can be easily ultrafine by laser heating and drawing the nylon 6 fibers under a minute applied tension.

[0061]

[Modification 1] In Example 2, the nylon 6 fiber was irradiated with the laser beam only once to heat and stretch the nylon 6 fiber. However, the nylon 6 fiber was irradiated with the laser beam in two steps to perform the laser heating. Ultrafine fibers can be obtained by stretching.

First, using the apparatus shown in FIG. 5, nylon 6 fibers were subjected to laser heating drawing under the conditions of applied tension σ _a = 36.7 MPa and laser power density = 17.3 W / cm ² . The diameter of the fiber obtained by such laser heating drawing was 87.5 μm, and the birefringence was 56.7 × 10 5.
It was ^-3 .

Then, the applied tension σ _a =
0.18 MPa, laser power density = 51.8 W / cm
Laser heating drawing was performed under the conditions of ² . The diameter of the obtained fiber was 1.9 μm, and an extremely fine fiber could be obtained. The birefringence was also 46.8 × 10 ⁻³ .
FIG. 8 shows an SEM photograph of such ultrafine fibers. As shown in FIG. 8, it can be seen that the nylon 6 fiber is extremely fine. As shown in this example, after irradiating a fiber with a predetermined tension with a laser beam to stretch it, a minute tension is applied to the fiber to irradiate the fiber with a laser beam to stretch the fiber, whereby the fiber can be made even finer. is there. In this example, the fiber was laser-heated and drawn under a predetermined tension, and then the obtained fiber was laser-heated and drawn under a slight tension. However, the fiber was laser-heated and drawn twice under a predetermined tension. After that, laser heating and stretching may be performed under a slight tension.

[Change in Diameter and Birefringence of Ultrafine Fiber] Next, regarding the fiber obtained by performing the laser heating drawing twice as described above, as in Example 1, the distance ΔL from the neck portion was measured. The changes in diameter and birefringence were examined. Fig. 15 shows the distance ΔL from the neck of the ultrafine fibers.
And the diameter and birefringence at the distance ΔL.

As can be seen from FIG. 15, the obtained fiber has a distance ΔL from the neck of 60 mm to 1500 mm.
In the range, the diameter is extremely thinned to 2 μm or less.
In particular, in the range of 60 mm to 1200 mm, it can be seen that extremely uniform ultrafine fibers are obtained with almost no change in diameter. On the other hand, the birefringence is the distance Δ from the neck.
40 × 10 in the range of L from 60 mm to 1480 mm
^It can be seen that it shows a high value of ^-3 or more. Particularly, when the distance ΔL from the neck portion is in the range of 200 mm to 1200 mm, it shows a high value of about 45 × 10 ⁻³ . Further, in this range, there is almost no change in the diameter, so it can be seen that ultrafine fibers that are uniform and have a small change in birefringence are obtained. Further, FIG. 15 shows a photograph of the neck portion of the fiber. As can be seen from the photograph, the neck portion is melted and expanded into a spherical shape, and the fiber is rapidly tapered from the spherical portion.

[0066]

Third Embodiment In this embodiment, it (isotacti
An example in which the laser heating drawing of the present invention is applied to c) -polypropylene (it-PP) will be described.

First, it- manufactured by Ace Polymer Co., Ltd.
PP pellets (Mw = 3 × 10 ⁵ , Mn = 5 × 10 ⁴ )
A fibril was prepared by melt spinning. The diameter of the fibrils is 408.6 μm, the birefringence is 0.3 × 10 ⁻³ ,
The crystallinity was 43.8%. When wide-angle X-ray diffraction was performed on the fibrils, it was confirmed from the wide-angle X-ray diffraction photograph that a Debye ring was observed, so that the fibrils were not oriented.

Next, the fibrils were laser heated and drawn using the apparatus shown in FIG. Laser power density 3
Fixed to 1.66 W / cm ² and applied tension of 0.022M
Pa, 0.030 MPa, 0.037 MPa, 0.04
Five types of fibers of 5 MPa and 0.06 MPa were obtained. Then, each of the obtained ultrafine fibers (SD (Small Diam
eter) fiber) and the diameter and birefringence were measured. The measurement results are shown in Table 1 below.

[0069]

[Table 1]

As can be seen from this table, fibers having a smaller fiber diameter are obtained as the applied tension becomes lower. Further, the birefringence also becomes higher as the fiber diameter becomes smaller, and it can be seen that the fiber has excellent crystallinity. The table also shows the draw ratio obtained from the fiber diameter. The draw ratio is 800 times or more, and the draw ratio increases as the applied tension decreases. Thus, polypropylene could also be made extremely fine by the laser heating drawing method of the present invention.

[0071]

Example 4 In this example, an example will be described in which the laser heating drawing of the present invention was applied after zone drawing of it-polypropylene (it-PP) fiber.

First, as in Example 3, it-PP pellets (Mw = 3 × 10 ⁵ , manufactured by Ace Polymer Co., Ltd.,
The fibrils were prepared by melt spinning Mn = 5 × 10 ⁴ ). The diameter of the fibrils was 408.6 μm, the birefringence was 0.3 × 10 ⁻³ , and the crystallinity was 43.8%. When wide-angle X-ray diffraction was performed on the fibrils, it was confirmed from the wide-angle X-ray diffraction photograph that a Debye ring was observed, so that the fibrils were not oriented.

Zone-stretching was performed on the fibrils by using a zone-stretching device 90 as shown in FIG. In the zone stretching device 90, the fibrils are supported by a pulley 96 provided at the right end of the support 91 with a weight attached to one end thereof, and then the other end of the fibril is provided at the left end of the support 91. Attached to the wall member 95. As a result, the fibrils are horizontally stretched above the support base 91 with a predetermined tension. The zone stretching device 90 is provided with a linear motor 92 on a support base 91.
Can move the rail 94 in the horizontal direction.
As shown in FIG. 9, a zone heater 93 is provided at the left end of the rail 94. By driving the linear motor 92, the zone heater 93 is moved relative to the fibrils at a predetermined speed. However, the fibrils can be heated at a predetermined temperature. The zone heater 93 has
As shown in FIG. 13, a heating body having a U-shaped cross section perpendicular to the length direction was used. Both the width d and the length of the slit portion 93a of the zone heater 93 are about 5 mm, and the fibers move inside the slit portion 93a. Zone heater 93
A nichrome wire is provided inside the fiber, and the fiber can be heated by energizing the nichrome wire. Using such a zone drawing apparatus, zone drawing was carried out at a drawing temperature of 140 ° C., an applied tension (σ _a ) of 7.8 MPa, and a moving speed (processing speed) of the heating element with respect to the fibrils of 100 mm / min. The fiber obtained by such zone drawing (hereinafter referred to as ZD (Zone Drawing) fiber) has a diameter of 131.1 μm and a birefringence of 34.0 × 10 ^−3.
Is.

Next, using the apparatus shown in FIG. 5, the laser power density PD was fixed at 39.57 W / cm ² , the applied tension σ _a was variously changed, and the ZD fiber was laser-heated and drawn to obtain an ultrafine fiber ( Hereinafter, SD (Small Diameter) fiber was obtained. Table 2 below shows the diameter, birefringence and draw ratio of each of the fibril, ZD fiber and SD fiber.

[0075]

[Table 2]

As can be seen from Table 2, after zone stretching,
The SD fiber obtained by performing the laser heating drawing is an extremely fine fiber having a diameter of 1.8 μm or less, and is finer than the fiber produced in Example 3 only by the laser heating drawing without zone drawing. There is. Also, SD
The draw ratio of the fiber was more than 50,000 times. ZD fiber with σ _a = 0.145 MPa, PD = 39.57 W / cm
^{When the} laser heating drawing was carried out under the drawing conditions of No. ² , the finest SD fiber having a diameter of 1.61 μm was obtained, and its birefringence was 28.4 × 10 ⁻³ . SE of such SD fiber
The M photograph and the SEM photograph of the fibrils are shown in FIG. As shown in FIG. 10, it can be seen that the SD fiber is extremely thin. No surface deterioration due to laser ablation was confirmed for the SD ultrafine fibers, and the fiber diameter was uniform.

FIG. 11 shows wide-angle X-ray diffraction photographs of the fibrils, ZD fibers, SD fibers, and ultrafine fibers produced only by laser heating drawing without zone drawing. Debye rings are observed in the fibrils, indicating that they are non-oriented. Sharp diffraction points were observed in the ZD fiber obtained by zone-drawing such a raw fiber, and it was confirmed that the fine crystals were highly oriented. Ultrafine fibers obtained by laser heating and drawing ZD fibers have weaker diffraction intensity than ZD fibers.
Diffraction points were observed similarly to the fibers, and the presence of oriented fine crystals could be confirmed.

FIG. 12B shows a polarization microscope photograph of the neck portion of the SD fiber. Further, FIG. 12 (A) shows a polarization microscope photograph of the neck portion of the fiber produced in Example 3.
As can be seen from FIG. 12 (A), in the case of only the laser heating drawing of Example 3, the fiber was tapered from the neck portion of the fibril, but the fiber obtained by the zone drawing of the present example was laser-heated. When stretching is performed, as shown in FIG. 12B, a spherical fused portion is formed in the neck portion, and the spherical portion is sharply tapered. From this,
Since the fiber was crystallized to some extent by zone drawing,
It is considered that the fibers are extra fine according to the above-mentioned principle.

[Changes in Diameter and Birefringence of Ultrafine Fibers] Next, with respect to the above-mentioned SD fibers, as in Example 1, changes in diameter and birefringence with respect to the distance ΔL from the neck portion were examined. FIG. 16 shows the distance ΔL from the neck portion of the SD fiber and the diameter and birefringence at the position of the distance ΔL.

As can be seen from FIG. 16, the SD fiber has an extremely fine diameter of 2 μm or less when the distance ΔL from the neck portion is in the range of 60 mm to 800 mm. Especially 6
It can be seen that in the range of 0 mm to 800 mm, there is almost no change in diameter, and extremely uniform ultrafine fibers are obtained. In the range where a diameter of 2 μm or less is obtained, S
It can be seen that the birefringence of the D fiber shows a high value of 25 × 10 ⁻³ or more. Further, in this range, there is almost no change in the diameter, so it can be seen that ultrafine fibers that are uniform and have a small change in birefringence are obtained. In addition, FIG. 16 shows a photograph of the neck portion of the fiber. As can be seen from the photograph, the neck portion expands into a spherical shape due to melting, and the fiber is sharply tapered from the spherical portion.

By applying laser heating drawing to it-PP fibers highly oriented by zone drawing as in this example, it is possible to easily produce ultrafine fibers having high orientation and extremely small fiber diameter. You can

[0082]

Fifth Embodiment FIG. 17 shows another specific example of the manufacturing apparatus according to the present invention. The manufacturing apparatus 600 mainly includes the fiber delivery device 6
1, a moving pulley 65, a fiber winding device 67, a control device 70, and a laser light source 71. The fiber delivery device 61 includes a reel 63 around which the fibrils are wound, and a rotation drive device 62 that rotationally drives the reel 63. By rotating the reel 63 at a predetermined speed by the rotation drive device 62, The fibrils wound around the reel 63 can be sent out at a predetermined speed.

The fibers delivered from the fiber delivery device 61 are supported by a fixed pulley 64 for support, and then wound around a moving pulley 65 arranged below the fixed pulley 64 to be fixed pulleys 64 and 65. It is urged to stretch in the vertical direction between. The other end of the fiber is diverted by the moving pulley 65, and then the alignment support portion 6 provided above the moving pulley 65.
It is wound by the fiber winding device 67 via 6.

The fiber winding device 67 includes a reel 68 for winding the fiber, and a rotation drive device 69 for rotating the reel 68. The other end of the raw fiber sent from the fiber delivery device 61 is attached to the reel 68, and the fiber can be wound around the reel 68 by rotationally driving the reel 68 at a predetermined rotational speed by the rotary drive device 69. it can. The control device 70 uses the fiber delivery device 61.
By controlling the rotation driving device 62 of the fiber winding device 67 and the rotation driving device 69 of the fiber winding device 67, the speed of the fiber sent from the reel 63 of the fiber feeding device 61 and the speed of the fiber wound by the reel 68 of the fiber winding device 67 are controlled. Can be adjusted. Thereby, the relative speed of the fiber with respect to the laser light emitted from the laser light source 71 and the tension applied to the fiber stretched between the fixed pulley 64 and the moving pulley 65 can be adjusted.

In the movable pulley 65, the rotation axis thereof is the guide portion 72.
Is vertically slidably engaged with the guide groove 73. The movable pulley 65 is held at a predetermined height h by the balance between the gravity and the tension of the fiber. Therefore, by maintaining the height position of the moving pulley 65 constant, the fixed pulley 6
It is possible to apply a constant tension to the fiber stretched between 4 and the movable pulley 65. Moreover, the weight of the movable pulley 65 can be appropriately selected so that the tension applied to the fibers is 1 MPa or less. Further, the movable pulley 65 is provided with a sensor (not shown) for measuring the height from the floor surface. The controller 70 controls the fiber winding device 67 based on the height position of the movable pulley 65 from the floor measured by the sensor.
The rotation speed of the reel 68 can be adjusted so that the height h of the moving pulley 65 from the floor surface is always constant. As a result, a constant tension can always be applied to the fiber. The frictional force generated between the rotating shaft of the movable pulley 65 and the guide groove is preferably as small as possible. For example, the movable pulley 65 may be configured to move linearly on the guide groove.

The laser light source 71, the shutter 74, the power meter 76 and the detector 75 are respectively shown in FIG.
The manufacturing apparatus 500 shown in FIG.

In the manufacturing apparatus 600, when the fibril is irradiated with the laser light from the laser light source 71, the fibril is stretched. When the fiber is stretched, the movable pulley 65 moves vertically downward due to gravity. At this time, the control device 70 detects the movement of the moving pulley 65 in the vertically downward direction by a sensor provided in the moving pulley 65, and winds the fiber so that the moving pulley 65 has a constant height position from the floor surface. Adjust the rotation speed of the device reel. In this way, the ultrafine fibers heated and stretched by laser can be wound on the reel of the fiber winding device.

Although the present invention has been specifically described with reference to the examples, the present invention is not limited to these. In the above example, the laser light was irradiated in a state where the fibrils were suspended, but the fibrils may be placed, for example, on a horizontal mounting table, and the fibrils may be horizontal to perform the laser heating drawing of the present invention. it can.

In the manufacturing apparatus shown in the fifth embodiment, the tension applied to the fibers is controlled to 1 MPa or less by adjusting the weight of the movable pulley 65 itself.
For example, by providing a counterbalance (balance weight) to the moving pulley and adjusting the weight of the counterbalance, the tension applied to the fibers by the moving pulley can be finely adjusted. That is, as shown in the schematic sectional view of the guide portion of FIG.
1, 92 are respectively provided, and the rope 94 having the counter balance 93 connected to one end is hung on the fixed pulleys 91 and 92, and the other end of the rope 94 is attached to the rotation shaft of the movable pulley 65 so as not to prevent the rotation of the movable pulley 65. Connect to the part. By providing such a counter balance 93, the weight of the moving pulley 65 is not limited in order to give a constant tension to the fibers, and it is possible to use a moving pulley having an arbitrary weight. For example, by selecting the weight of the counterbalance so that the difference between the weight of the movable pulley and the weight of the counterbalance is small, it is possible to apply extremely minute tension of 1 MPa or less to the fiber. Further, instead of such counter balance, it is possible to give a minute tension to the fiber by, for example, using a spring or the like to urge the moving pulley upward to reduce the downward force of the moving pulley. .

The production apparatus shown in Example 5 is a specific example of an apparatus for producing one ultrafine fiber. However, by changing such an apparatus as described below, a plurality of ultrafine fibers can be simultaneously produced. It can be manufactured. That is,
The fixed pulley for supporting the fibers is configured by using, for example, a wide fixed pulley divided into a plurality of fiber winding regions so that the plurality of fibers can be supported at regular intervals. Also,
The fiber delivery device is configured to provide a plurality of coaxial reels and deliver the fiber from each reel. Alternatively, a plurality of fibers may be individually delivered at regular intervals by using a wide reel whose fiber delivery portion is partitioned in the axial direction. The plurality of fibrils fed from the fiber feeding device are supported by the wide fixed pulley described above. Movable pulleys also hold multiple fibers side by side at regular intervals,
For example, it may be configured by using a movable pulley that is wide in the axial direction. The fiber take-up device may also be configured to use a plurality of coaxial reels to wind the fiber at a moving speed on each reel. Alternatively,
A wide reel whose fiber winding portion is partitioned in the axial direction may be used to individually wind a plurality of fibers at regular intervals. A plurality of laser light sources may be used to irradiate each fibril with a laser beam.
By providing a cylindrical lens having a rotation axis in the direction in which a plurality of fibers are arranged on the optical path of the laser light using a laser light source of a table, the laser light becomes elongated in the direction perpendicular to the axial direction of the fibers. Therefore, each fiber can be irradiated with laser light. Instead of such a cylindrical lens, a polygon mirror may be used to sequentially irradiate each fiber with laser light. By improving the apparatus as described above, it becomes possible to draw a plurality of fibers by laser heating at one time. The manufacturing apparatus having such a configuration is excellent in productivity.

[0091]

According to the production method of the present invention, ultrafine fibers having excellent orientation and crystallinity can be produced extremely easily, so that ultrafine fibers having high strength can be provided at low cost.

The nylon 6 fiber, polypropylene fiber and PET fiber of the present invention have high birefringence even though they are extremely fine, and therefore have higher strength than conventional ultrafine fibers and are excellent in handleability and processability.

Since the manufacturing apparatus of the present invention can realize the manufacturing method of the present invention, it is possible to extremely easily manufacture ultrafine fibers having excellent orientation and crystallinity.

[Brief description of drawings]

FIG. 1 is a graph of fiber diameter versus applied tension applied to PET fibrils during laser heating drawing.

FIG. 2 is a graph of fiber birefringence against applied tension applied to PET fibrils during laser heating drawing.

FIG. 3 (A) is a 350 times SEM photograph of PET fibrils and ultrafine fibers obtained by laser heating and drawing of the present invention, and FIG. 3 (B) is 10,000 times SE of ultrafine fibers.
It is an M photograph.

FIG. 4 is a graph showing changes in fiber diameter with respect to laser power density when various fiber moving speeds with respect to laser light are changed.

FIG. 5 is a schematic configuration diagram of a manufacturing apparatus according to the present invention.

FIG. 6 (A) is a graph showing changes in fiber diameter with respect to laser power density of nylon 6 fibers, and FIG. 6 (B) is a graph showing changes in fiber birefringence with respect to laser power density. Is.

FIG. 7 shows an SEM photograph of nylon 6 ultrafine fibers produced in Example 2.

FIG. 8 shows an SEM photograph of nylon 6 ultrafine fibers produced by irradiating laser light twice in Modification 1.

FIG. 9 is a schematic configuration diagram of a zone heating and stretching apparatus used in Example 4.

FIG. 10 is a SEM photograph of polypropylene fibrils and SD fibers obtained by laser heating and drawing the fibrils.

FIG. 11: polypropylene fibrils, ZD fibers produced by zone-drawing the fibrils, SD fibers produced by laser-drawing the ZD fibers, and laser-drawing without zoning the fibrils. The wide-angle X-ray-diffraction photograph of the produced ultrafine fiber is shown.

12 (A) is a polarization microscope photograph of the neck portion of the PP ultrafine fiber produced in Example 3, and FIG.
(B) is a polarization microscope photograph of the neck portion of the SD fiber produced in Example 4.

13 is a schematic configuration diagram of a zone heater of the zone stretching apparatus shown in FIG.

FIG. 14 is a graph showing changes in diameter and birefringence with respect to the distance ΔL from the neck portion of the ultrafine fibers manufactured in Example 1.

FIG. 15 is a graph showing changes in diameter and birefringence with respect to the distance ΔL from the neck portion of the ultrafine fibers manufactured in Modification 4.

16 is a graph showing changes in diameter and birefringence with respect to the distance ΔL from the neck portion of the it-polypropylene ultrafine fiber produced in Example 4. FIG.

FIG. 17 is a schematic configuration diagram of a manufacturing apparatus according to the present invention used in Example 5.

FIG. 18 is a distance Δ from a fibril portion of the ultrafine fiber produced by laser heating and drawing, which starts to become thin.
It is a figure for explaining L.

FIG. 19 is a structural example in which a counterbalance is provided for the moving pulley of the manufacturing apparatus shown in FIG.

[Explanation of symbols]

51 Carbon dioxide laser oscillator 52 detector 53 power meter 54 shutter 55 Fiber moving device 56 pulley 57 Crosshead 58 Guide rail 59 Support rod 60 weights 90 zone stretching device 93 zone heater 500,600 Manufacturing equipment

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) D01F 6/62 303 D01F 6/62 303J

Claims (26)

[Claims] 1. A method of drawing a fiber by irradiating the fiber with a laser beam while applying a tension of 1 MPa or less. 2. The method according to claim 1, wherein the power density of the laser light with which the fiber is irradiated is 15 W / cm ² or more. 3. The method according to claim 1, wherein the laser light is moved relative to the fiber. 4. A vertical support for the fibers.
4. The method according to any one of 3 to 3. 5. The method according to claim 1, wherein the fiber is irradiated with the laser light a plurality of times. 6. The method according to claim 1, wherein the laser light is irradiated after the fiber is zone-stretched. 7. The method according to claim 1, wherein the fiber is one selected from the group consisting of polyethylene terephthalate, nylon 6 and polypropylene. 8. A drawn fiber obtained by the method according to claim 1. 9. The drawn fiber according to claim 8, wherein the fiber is composed of a thermoplastic polymer. 10. The drawn fiber according to claim 9, wherein the drawn fiber has a diameter of 5 μm or less and has a birefringence within a range of 25 × 10 ^{−3 to} 120 × 10 ⁻³ . 11. The stretched fiber according to claim 10, wherein the thermoplastic polymer is one selected from the group consisting of nylon 6, polypropylene and polyethylene terephthalate. 12. Nylon 6 fiber having a diameter of 2 μm or less and a birefringence of 40 × 10 ⁻³ or more.
Nylon 6 fiber characterized by being in the range of 50 × 10 ⁻³ . 13. A polypropylene fiber having a diameter of 2 μm or less and a birefringence of 25 × 10 ⁻³ or more.
A polypropylene fiber characterized by being in the range of 35 × 10 ⁻³ . 14. The polypropylene fiber according to claim 13, which has a crystal orientation coefficient of 0.9 or more. 15. A polyethylene terephthalate fiber having a diameter of 5 μm or less and a birefringence of 70 × 10 ⁻³ to.
A polyethylene terephthalate fiber characterized by being in the range of 120 × 10 ⁻³ . 16. A manufacturing apparatus for manufacturing ultrafine fibers, comprising a laser light source for irradiating the fibers with laser light, and a fiber moving device for moving the fibers relative to the laser light. Manufacturing apparatus comprising. 17. The manufacturing apparatus according to claim 16, further comprising a holding portion for holding a part of the fibers and applying a tension of 1 MPa or less to the fibers. 18. The manufacturing apparatus according to claim 16, wherein the fiber moving device includes a supporting portion that supports one end of the fiber, and the supporting portion is moved relative to the laser light. 19. The manufacturing apparatus according to claim 18, wherein the supporting portion supports the fibers in the vertical direction, and the fiber moving device moves the fibers in the vertical direction. 20. The slider device according to claim 1, wherein the fiber moving device includes a movable slider connected to the support portion and a guide portion for movably guiding the movable portion.
The manufacturing apparatus according to 8 or 19. 21. The supporting part is a supporting part for supporting a plurality of fibers at the same time, and further, the cylindrical part for irradiating the plurality of fibers supported by the supporting part with a laser beam from the laser light source, respectively. The manufacturing apparatus according to claim 18, further comprising a lens or a polygon mirror. 22. The fiber moving device includes a fiber delivery device for delivering the fiber, and a fiber winding device for winding the delivered fiber, and a speed for delivering the fiber from the fiber delivery device, The manufacturing apparatus according to claim 16 or 17, wherein the relative speed of the fiber with respect to the laser light is controlled by controlling the speed at which the fiber is wound by the fiber winding device. 23. The manufacturing apparatus according to claim 22, wherein the holding portion is a moving pulley, and the fiber delivered by the fiber delivery device is wound by the fiber winding device via the moving pulley. 24. A sensor for measuring the height position of the moving pulley is provided, and the height position of the moving pulley becomes constant based on the height position of the moving pulley measured by the sensor. The manufacturing apparatus according to claim 23, wherein the winding speed of the fiber is controlled by the fiber winding device. 25. A guide rail for guiding the moving pulley is provided, and the fiber winding device controls the winding speed of the fiber so that the position of the moving pulley on the guide rail becomes constant. Item 23. The manufacturing apparatus according to Item 23. 26. The fiber delivery device delivers a plurality of fibers individually, and the fiber winding device winds a plurality of fibers,
The manufacturing apparatus according to any one of claims 22 to 25, further comprising a cylindrical lens or a polygon mirror for irradiating each of the plurality of fibers delivered from the fiber delivery device with a laser beam from the laser light source.