JP5134417B2 - Method for producing polyester multifilament - Google Patents

Description

  The present invention relates to a method for producing a polyester fiber, and more particularly to a method for producing a polyester multifilament having unprecedented mechanical properties.

  Polyester fibers have excellent balance in mechanical properties and dimensional stability, and can be manufactured at low cost by melt spinning / drawing and high-speed spinning, so they are widely used not only for clothing but also for industrial use. ing.

  When polyester fibers are used for industrial applications, the most important characteristic is that of mechanical characteristics such as high strength, and there is an increasing demand for further improvement of mechanical characteristics in order to expand the applications.

In general, a method for producing a fiber using a polyester resin is obtained by melting a polyester resin and guiding it to a melt spinneret pack attached to a spin block, melting and discharging the resin from the melt spinneret pack, It is well known that it is carried out in a melt spinning process which is cooled and solidified and taken up by a take-up roller. In addition, rubber cords such as tire cords, rubber hoses, rubber belts, belts such as seat belts, slings, nets such as fish nets and land nets, ropes, and other industrial polyester fibers that require high mechanical properties are generally used. Specifically, it is manufactured by a method in which a raw material resin having a high degree of polymerization is melt-spun and then stretched at a high magnification and heat-set as necessary. The obtained fiber is required to have a high breaking strength while having an appropriate breaking elongation. This characteristic is referred to as toughness and is expressed as strength × (elongation) ^½ .

  In order to improve the strength, one of the techniques is to make the molecular chain as low-oriented as possible in the undrawn yarn stage and to make a highly oriented fiber by performing high-magnification drawing in the drawing process.

Laser irradiation is known as one of the low orientation techniques. The resin can be heated instantaneously by laser irradiation, and the orientation can be lowered by lowering the melt viscosity. In polyester melt spinning, excellent stretchability, that is, low orientation, is achieved by irradiating a traveling resin with an energy density of 20 W / cm ² or more at a position from the spinneret surface to 15 cm along the spinning line. The inventors have disclosed a method for obtaining an undrawn yarn (see Patent Document 1: pages 2 to 4). However, in order to obtain fibers with a lower orientation, there is a problem that when a strong laser irradiation is performed, the polyester resin is decomposed and the strength of the obtained fibers is lowered. The strength of the resulting fibers was not sufficient.

  Further, a technique is known in which a single-sided heating and a single-sided cooling of a yarn are simultaneously performed by irradiating a laser until the thinning of the yarn is substantially finished (see Patent Document 2). In this technique, the intrinsic viscosity of the resin used is at most about 0.63 (see Patent Document 2: page 3), and a powerful laser (100 to 300 W in the examples) while cooling one side of the spinning line. By irradiating the other side of the yarn for a short time, a structural difference in the cross-sectional direction is forcibly generated, so that the strength of the obtained fiber is at a very low level.

  Moreover, in laser irradiation, a method for defining the laser to be irradiated and the diameter of the nozzle hole has been proposed (Patent Document 3). Although this method certainly has the effect of improving the mechanical properties of the yarn, In spinning, a difference in strength between single yarns is produced, so that fibers having satisfactory physical properties could not be obtained depending on applications.

As described above, the polyester fiber obtained by the melt spinning method is known, but there is still no method for producing a polyester multifilament having high strength and high toughness in this fiber.
JP 2004-324017 A (pages 1 and 2) Japanese Patent Publication No. 56-11762 (pages 1 to 3) JP 2006-038323 A (pages 1 and 2)

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a method for producing a polyester multifilament having unprecedented mechanical properties.

  As a result of intensive studies on the thinning behavior of polyester in melt spinning at high temperatures, the present inventors have been able to heat the resin by laser irradiation and promote the thinning behavior at high temperature in high molecular weight polyester resins. The present inventors have found that a fiber having an unprecedented mechanical property can be obtained by affecting the formation of a polyester structure.

That is, first, the polyester multifilament obtained by the method for producing a polyester multifilament of the present invention will be described.
Polyester multifilaments obtainable by the process for producing a polyester multifilament of the present invention is obtained by melt spinning, made of single yarns 6 or more and is characterized by satisfying the following requirements 1 to 4 at the same time.
1. Strength ≧ 9.0 cN / dtex,
2. Elastic modulus ≧ 130 cN / dtex,
3. Toughness ≧ 30,
Toughness = Strength x (Elongation) ^1/2
4). Satisfying the following formulas (a) and (b):
S _m : m-th single yarn strength (cN / dtex) among m multifilaments
m ≧ 6

The method for producing a polyester multifilament according to the present invention uses a spinneret having 6 or more holes, melt-spins a polyester resin having an intrinsic viscosity of 0.8 g / dl or more, and 100 mm from the spinneret along the spinning line. The melt spinning method in which the laser is irradiated to all the discharged yarns until the laser, and the laser irradiated to a certain discharged yarn or the laser not irradiated to any discharged yarn is reflected by the mirror, thereby each discharged yarn. The laser beam is irradiated from three or more different directions so as to satisfy the following expressions (c) and (d), and at least one of the mirrors reflects or transmits the laser in a plurality of directions. To do.

According to the method for producing a polyester multifilament according to the first aspect of the present invention , there is provided a polyester multifilament having unprecedented mechanical properties.

Embodiments of the method for producing a polyester multifilament of the present invention will be described below.

  The polyester resin used in the present invention is a linear polymer having an ester bond in a repeating structure, has a good balance of mechanical properties and dimensional stability, and has excellent properties such as melt spinning / drawing and high speed. Since it can be manufactured at low cost by spinning, it is a resin with a wide range of industrial applications. The polyester resin is not particularly limited, but polyethylene terephthalate, polypropylene terephthalate, and polybutylene terephthalate are preferable because of their high versatility, and polyethylene terephthalate is more preferable for achieving high strength. The polyester resin used in the present invention may be copolymerized with other components as long as the effects of the present invention are not impaired. Furthermore, the polyester resin used in the present invention may contain a small amount of known additives such as a matting agent, a flame retardant, and a lubricant.

The polyester multifilament obtained by the method of the present invention simultaneously satisfies the following requirements 1 to 4 obtained by melt spinning as described above , and the features thereof are as follows.

1. Strength ≧ 9.0 cN / dtex,
Considering the quality level required as a structural material for industrial materials in the recent trend of high technology, the strength is required to be at least 9.0 cN / dtex. Further, in order to satisfy a high level of demand and to enable application expansion in industrial materials, it is preferably 10.0 cN / dtex or more. According to the method of the present invention, a material satisfying these levels can be produced . The upper limit is preferably 20 cN / dtex, which is considered to be close to the upper limit that can be substantially produced by the method of the present invention.

2. Elastic modulus ≧ 130 cN / dtex,
In industrial material applications, stretching and compression are often repeated, and fibers with a low elastic modulus, that is, with a narrow elastic deformation region, undergo plastic deformation over time, resulting in deterioration of mechanical properties and breakage. Degradation progresses. For excellent stress elongation compression if fibers having a modulus of elasticity can play an elastically deformable, plastic deformation is small, Ru can minimize the deterioration of the fibers and structural material. The polyester fiber obtained by the method of the present invention has an elastic modulus of 130 cN / dtex or more, and can achieve 150 cN / dtex or more. The upper limit of the resulting elastic modulus is preferably 250 cN / dtex which is considered to be close to the limit level that can be substantially manufactured.

3. Toughness ≧ 30,
Fibers used for industrial materials are required to have a large energy absorption rate even under high stress. This is a characteristic generally regarded as toughness, and is represented by strength × (elongation) ^1/2 . In the present invention , the unit of strength is cN / dtex, and the unit of elongation is a value derived from a value of%. Is used. In industrial material applications such as belt reinforcements, tire cords, and ropes, the stress applied to the single fibers may increase momentarily, and the resulting breakage of the single fibers in the structural material Incurs a decline. Furthermore, under conditions where stretch and compression are repeatedly applied under high stress such as a rope, if the single fiber has low toughness, the structural material easily deteriorates due to abrasion or deformation. In order to suppress such deterioration, it is necessary that the toughness is 30 or more, and in order to make this characteristic remarkable, the toughness is preferably 35 or more, and the polyester obtained by the method of the present invention Multifilaments meet these standards. The upper limit of the toughness of the polyester multifilament obtained by the method of the present invention is preferably 60, which is considered to be close to the limit level that can be substantially produced by the method of the present invention.

4). Satisfying the following formulas (a) and (b):
S _m : m-th single yarn strength (cN / dtex) among m multifilaments
m ≧ 6

As a fiber used for industrial material applications, it is necessary that the multifilament itself has high strength, and for this purpose, it is necessary that there is no difference in mechanical properties between single yarns. Usually, the higher the uniformity between the single yarns constituting the multifilament, the higher the strength of the multifilament. For this reason, it is important that the multifilament is composed of 6 or more filaments, and the variation in the strength value of the single yarn (one filament) defined by the formula (a) is 0.3 or less. In order to exhibit strength more effectively, it is more preferably 0.15 or less, and the polyester multifilament obtained by the method of the present invention satisfies these levels. The lower limit is preferably 0.001, which is considered to be close to the limit that can be substantially produced by the method of the present invention. Further, the larger the number of fibers constituting the multifilament, the greater the absolute amount of strength required to break the multifilament, which is preferable. However, the optimum number can be selected depending on the application. Its upper limit is preferably 2,000, which is considered to be close to the limit levels that can substantially produced by the method of the present invention.

In the method for producing a polyester multifilament of the present invention , a high-temperature molten resin discharged from a spinneret is irradiated with a laser and heated instantaneously to increase the deformation rate at high temperatures. Therefore, it is necessary to irradiate the resin with a laser having an appropriate intensity up to 100 mm. This is because, since the resin temperature is sufficiently high from the spinneret to 100 mm, high-temperature deformation is easily promoted by laser irradiation, and laser irradiation can be performed stably with almost no yarn shaking. In addition, when powerful laser irradiation is performed at a position distant from 100 mm, pulsation associated with heating spots occurs, and physical property spots occur in the fiber axis direction, resulting in a decrease in strength of the obtained fiber. . From this point of view, it is more preferable to irradiate between 50 mm from the spinneret where the temperature of the resin is higher and the yarn swing is less. In order to increase the heating efficiency at the irradiation position and increase the resin temperature, the spinneret More preferably, the irradiation is performed immediately after the discharge, that is, at 0 mm. In the present invention, the spinneret surface means a position where the discharged resin has a free surface and can be deformed by extension.

  In the present invention, it is necessary to irradiate each discharge yarn with a laser from three or more different directions, and by irradiating the laser from three or more different directions, the resin can be sufficiently heated while suppressing thermal decomposition, The discharged yarn has a small structural difference in the cross-sectional direction and uniform mechanical characteristics, and a multifilament with excellent strength can be obtained. The number of irradiation lasers is not particularly limited, but in order to further increase the strength of the fiber, it is preferable to perform laser irradiation from six or more directions. As an upper limit, it is 100 directions considered as the limit of the direction which can be irradiated substantially.

  That at least one of the mirrors reflects the laser in a plurality of directions refers to a mirror that can be reflected in a plurality of directions when irradiated with the laser light substantially used in the present invention, and may be a complex of mirrors, You may provide the mechanism in which a sheet | seat reflects in multiple directions. The laser beam substantially used in the present invention has a diameter or width of 0.5 mm or more. By using the mirror, even when there are many ejection yarns, it becomes possible to easily irradiate each ejection yarn with a plurality of lasers, and the mechanical properties between the obtained multifilament single yarns are made uniform. .

In carrying out the method for producing a polyester multifilament of the present invention , it is preferable that the intensity distribution of the laser irradiated from at least one direction is made uniform . Here, uniformizing the intensity distribution means that the energy of the central part is reduced by using a homogenizer or the like for the laser light having a Gaussian intensity distribution in which the central part of the laser light is usually high energy. It shows that the intensity distribution of the laser beam is deformed. By irradiating laser with uniform distribution of intensity, each discharged yarn can be irradiated with laser uniformly, so that the strength, elastic modulus and toughness of the obtained multifilament are stabilized, and the mechanical properties between single yarns are made uniform. Therefore, it is preferable.

  In addition, the mirror used in the present invention is used in the vicinity of a discharge port for melt spinning and is placed in a high temperature atmosphere, and since several percent of the laser hitting the mirror becomes heat and is absorbed by the mirror, The mirror part may become hot. When the oligomer or the like is thermally deteriorated on the mirror that has become high in temperature, there is a problem that the mirror is likely to become dirty and each discharge yarn cannot be heated sufficiently. For this reason, in order to obtain a polyester multifilament stably by melt spinning, it is preferable to have a cooling mechanism in the mirror, such as passing cooling water around the mirror.

In order to make the effect of the present invention sufficient, it is important that the intrinsic viscosity of the polyester resin is 0.8 dl / g or more. This is to increase the breaking strength and toughness of the fiber obtained by increasing the intrinsic viscosity of the polyester resin. In order to further improve the breaking strength, the intrinsic viscosity is preferably 1.0 dl / g or more, and more preferably 1.2 dl / g. When the intrinsic viscosity is less than 0.8 dl / g, the breaking strength and the toughness level are lowered, and a yarn having sufficient physical properties cannot be obtained. The upper limit is preferably 3.0 dl / g, which is considered to be close to the upper limit that can be substantially produced by the production method of the present invention.

  The diameter of the spinneret hole diameter D (φcm) of the spinneret used in the present invention is not particularly limited as long as the resin can be stably discharged. However, in order to obtain high-strength fibers, it is preferably less than φ0.05 cm. . If it is less than φ0.05 cm, the resin is thinned in a high temperature state before discharging from the die. This is close to the object of the present invention in which the resin is heated and thinned by laser irradiation on the spinning line, and is preferable as a synergistic effect, and it is easy to achieve both improvement in strength and toughness when used as a drawn yarn. In addition, when the diameter of the nozzle hole is small, the fiber diameter becomes small at the position where laser irradiation is performed, and the laser absorption rate of the resin decreases, so that the laser irradiation to each discharge yarn tends to be uniform. For this purpose, the diameter of the nozzle hole is preferably φ0.03 cm or less. In the present invention, φ0.005 cm, which is considered to be substantially close to the lower limit at which resin can be discharged, is the lower limit. The diameter of the nozzle hole in the present invention is the outlet diameter of the discharge hole formed in the nozzle. When spinning with a modified hole, the value obtained by converting the sectional area of the discharge hole to a round hole is used.

  In the present invention, the laser light receiving length: l (cm) is the length in the fiber axis direction of the portion where the resin is substantially irradiated with the laser. In response to this, it is heated. The light receiving length is not particularly limited, but is preferably 0.2 cm or more in order to sufficiently heat the polyester resin, and is preferably 1 cm or less in order to stabilize the yarn forming property. .

The laser used in the present invention is a monochromatic light, a parallel light beam, and a coherent light beam. The energy density of the laser: E (W / cm ² ) is calculated by dividing the laser output measured at the position where the molten resin receives the laser by the spot area.

  The type of laser used in the present invention is not particularly limited. However, a carbon dioxide gas laser having a laser wavelength of 10.6 μm has a high absorption rate of the polyester resin and is efficient, and has a large output for industrial use. In view of this, a carbon dioxide laser is preferable.

  In the present invention, the discharge amount per single hole: Q (g / min) is the discharge amount of the resin per hole of the spinneret. Since the production method of the present invention is aimed at industrial fibers, the discharge amount per single hole of the resin is preferably 1.0 g / min or more, more preferably 2.0 g / min or more.

In the present invention, in order to lower orienting the fiber obtained by melt spinning, be irradiated is preferable to irradiate a strong laser to the resin, the laser moderate intensity from three or more directions along the spinline Is important . At this time, as a laser irradiated from one direction, a nozzle hole diameter: D (φcm), a laser light receiving length: l (cm), an i-th laser energy density: E _i (W / cm ² ), It is important that the value of the following formula (c) obtained from the discharge amount: Q (g / min) is 3 or less .

When the value obtained by the equation (c) is larger than 3, high-intensity laser irradiation is performed from any one direction, and the resin temperature of the light-receiving portion surface layer portion of the polyester resin becomes higher than necessary. . For this reason, thermal decomposition of the oligomer component contained in the resin occurs, and fine fibers are generated in the resulting fiber, and the fiber is melted by slight shaking of the discharged resin, so that the yarn forming property is deteriorated. Further, when high-intensity laser irradiation is performed, the intrinsic viscosity is lowered due to the thermal decomposition of the polyester resin itself, and the breaking strength and toughness of the resulting fiber are significantly lowered. For this reason, it is important to limit the amount of heat applied by laser irradiation from one direction so that the value obtained by the formula (c) satisfies 3 or less, in order to increase spinning stability and increase productivity. More preferably, the value obtained from the formula (c) is 2.5 or less.
On the other hand, in order to obtain a fiber having physical properties such as sufficient breaking strength and toughness, powerful laser irradiation is essential to sufficiently heat the resin on the spinning line. For this reason, it is important to perform laser irradiation from three or more directions so that the value calculated by the following formula (d) is three or more.

As described above, in the method for producing a polyester multifilament of the present invention , by performing laser irradiation from three or more directions, the spinning instability caused by laser irradiation from any one direction is eliminated, and the formula (d) is satisfied. A sufficient amount of heat can be applied to the resin by laser irradiation. Along with this, the unstretched fiber obtained has a low orientation, and after stretching, a fiber having high strength and high toughness can be obtained. Since heating the resin further increases the effect of the present invention, the value obtained by the formula (d) is more preferably 3.5 or more. The upper limit is 30 which is considered to be close to the limit at which spinning becomes practically difficult.

  The fiber whose thinning at a high temperature is promoted according to the present invention has sufficiently excellent mechanical properties, but further, a cooling delay measure which is a conventional method for the purpose of improving the yarn forming property and suppressing the orientation, so-called heating tube and heat insulation tube. It is preferable to use together.

  In the production method of the present invention, the fiber take-up method is not particularly limited, and any method such as a so-called two-step method and a direct drawing method can be adopted. However, when orientational crystallization occurs on the spinning line, the crystal becomes an inhibition point of orientation, which may reduce the effect of efficiently orienting molecular chains. Therefore, it is preferable to set the take-up speed so that orientation crystallization does not occur in the spinning process. Specifically, the take-up speed is preferably less than 1000 m / min. By setting it to less than 1000 m / min, the degree of orientation of unstretched fibers can be lowered, and high strength can be easily achieved. Furthermore, in order to make this tendency remarkable, it is preferable to set the take-up speed to 700 m / min or less. However, the lower limit of the take-up speed is preferably 300 m / min from an industrial viewpoint. The take-off speed of the present invention refers to the rotation speed of the first roller with which the molten resin contacts after cooling and solidification.

  In order to obtain fibers having excellent characteristics suitable for industrial fibers, in particular, strength, it is preferable to form a thermally stable fiber structure by orienting molecular chains by drawing heat setting. As a stretching method, for example, there is a method of stretching between a pair of rollers having different rotation speeds.

  In order to obtain excellent mechanical properties, it is preferable to stretch in two or more stages. The speed ratio and temperature between the rollers can be changed according to the required mechanical characteristics. The heating method can be selected from heating methods such as a heating roller, a hot plate, a heat pin, and laser beam irradiation. In addition, it is preferable to use a laser beam as a heating method in the stretching step because it can be stretched with high stress without generating an obstacle to molecular chain orientation such as microcrystals generated during heating in the stretching step. It is a technique.

Hereinafter, the production method of the polyester multifilament of the present invention will be described specifically and in detail with reference to Examples , Reference Examples and Comparative Examples.
1 and 2 are schematic views of an apparatus showing an embodiment of the method of the present invention. In the laser irradiation apparatus shown in FIG. 1, after each laser beam is irradiated to each discharge yarn F (filament), the laser beam is reflected by the mirror 1a in the two directions of the mirror 2a and the mirror 2d, and then irradiated to each discharge yarn. Is. The irradiation apparatus shown in FIG. 2 is one in which laser light is reflected in a plurality of directions by a mirror 1b and then irradiated to each ejection yarn F in space. 1 and 2 can be designed with a spread in the direction perpendicular to the plane of the paper.

  The physical property values in Examples and Comparative Examples were measured by the following methods.

A. After measuring the breaking strength, elongation, elastic modulus multifilament or single yarn weight to determine the fineness of the fiber, using an autograph manufactured by Shimadzu Corporation, the initial sample length is 50 mm (unstretched fiber), 100 mm (stretched fiber) ), A stress-strain curve was measured at a tensile rate of 100% / min, and the breaking strength, elongation, and elastic modulus of the multifilament or single yarn were determined, respectively. The average value measured twice was used for the measurement of fiber fineness. As the stress-strain curve, an average value measured five times was used.

B. With the laser strength resin not running, a laser power meter (manufactured by OPHIR) was installed at the resin running position to measure the laser irradiation energy, and this was measured with a laser beam profiler (manufactured by SPIRICON). Divided by the laser spot area at the time of irradiation. This was performed twice, and the average value was taken as the laser intensity.

C. Intrinsic Viscosity Samples are heated at 160 ° C. for 20 minutes, dissolved in an orthochlorophenol solution, and measured at 25 ° C. using an Ostwald viscometer. In this example, Shodex GPC-101 manufactured by Showa Denko KK was used to measure the eluent HFIP, column HFIP-806M × 2, detector RI, flow rate 1.0 mL / min, and polyethylene terephthalate with a known intrinsic viscosity. Conversion was performed using (IV = 0.6, 0.8, 1.7). This was performed twice, and the average value was defined as the intrinsic viscosity.

Example 1
Polyethylene terephthalate (inherent viscosity: 1.0 dl / g) was melted by a biaxial extruder and discharged at a spinning temperature of 320 ° C. and a spinneret (hole diameter φ0.03 cm, number of holes 6) at a single hole discharge rate of 3.0 g / min. At a position 15 mm downstream from the spinneret surface, a carbon dioxide laser with a laser intensity of 250 W / cm ² is irradiated from six directions to a spot with a laser receiving length of 0.4 cm using the apparatus shown in FIG. The yarn was taken up at a spinning speed of min to obtain an undrawn yarn. The unstretched yarn is guided to a supply roller, and after two-stage stretching is performed between the first stretching roller, the second stretching roller, and the third stretching roller, the final roller is passed through a tension control type winder, A drawn yarn was obtained. The temperature of each stretching roller was 90 ° C., 140 ° C., and 230 ° C., the stretching ratio in the second stage was set to 1.6 times, and the stretching speed was set to 100 m / min. Table 1 shows the physical properties of the obtained polyester fibers.

Example 2
Except that the intrinsic viscosity of the resin used was 1.2 dl / g and the spinning temperature was 330 ° C., yarn was produced in the same manner as in Example 1 to obtain a drawn yarn. Table 1 shows the physical properties of the obtained polyester fibers.

Example 3
Spinning was performed in the same manner as in Example 1 except that the number of holes in the spinneret used was 36, the single hole discharge rate was 2.0 g / min, and the laser was irradiated from three directions to obtain drawn yarns. Table 1 shows the physical properties of the obtained polyester fibers.

Example 4
Except that the laser beam before irradiating the yarn was passed through a homogenizer and the intensity distribution was made uniform, yarn production was performed in the same manner as in Example 1 to obtain a drawn yarn. Table 1 shows the physical properties of the obtained polyester fibers. By making the laser intensity uniform, interstitial spots in the obtained drawn yarn were reduced, and more excellent fibers were obtained.

Reference example 1
Except for irradiation with a carbon dioxide laser with a laser intensity of 100 W / cm ² , all yarns were produced in the same manner as in Example 1 to obtain drawn yarns. Table 1 shows the physical properties of the obtained polyester fibers.

Comparative Example 1
Except for irradiating a carbon dioxide laser with a laser intensity of 250 W / cm ² from one direction, yarn was produced in the same manner as in Example 1 to obtain a drawn yarn. Table 1 shows the physical properties of the obtained polyester fibers.

Comparative Example 2
Except for irradiating a carbon dioxide laser with a laser intensity of 1000 W / cm ² from one direction, yarn was produced in the same manner as in Example 1 to obtain a drawn yarn. Table 1 shows the physical properties of the obtained polyester fibers.

From the results of Examples, Reference Examples, and Comparative Examples shown in Table 1, the strength, elastic modulus, and toughness of the drawn yarn are increased by irradiating laser from three or more directions, and high strength effective for industrial use. It can be seen that fibers are obtained. Furthermore, in Examples 1 to 4, the strength, the elastic modulus, and the toughness are increased as compared with Reference Example 1 by irradiating each discharge yarn with the high energy laser represented by Formula 4. Further, in Example 4, by uniformizing the laser intensity distribution, the single yarn unevenness represented by the formula (a) is reduced, stably performing, and industrially effective for a wide variety of uses. The fiber is easy to use. As described above, the polyester fiber according to the present invention has high strength and high toughness.

An example of an apparatus that irradiates each discharged yarn with laser from six directions that can be used when carrying out the method of the present invention is shown. As an apparatus that can be used when carrying out the method of the present invention, an example of an apparatus using a mirror that reflects a laser in a plurality of directions is shown.

Explanation of symbols

L: Laser beam F: Discharge yarn (filament)
1a, 1b: Reflecting mirrors 2a-2m in a plurality of directions: Mirror

Claims (3)

Using a spinneret having 6 or more holes, a polyester resin having an intrinsic viscosity of 0.8 g / dl or more is melt-spun , and a laser is applied to all discharged yarns between the spinneret and 100 mm along the spinning line. a melt spinning method of irradiating, by reflecting a laser in a laser or any discharge yarn was irradiated on the discharge thread is not irradiated with the mirror, the laser from three or more different directions to respective discharge yarn, below A method for producing a polyester multifilament, wherein irradiation is performed so as to satisfy the expressions (c) and (d), and at least one of the mirrors reflects or transmits a laser in a plurality of directions.
n ≧ 3
D: Diameter of base hole (cm)
l: Laser receiving length (cm)
E _i : energy density (W / cm ² ) of the i-th laser irradiated to a certain discharge yarn
Q: Discharge amount per single hole (g / min) The method for producing a polyester multifilament according to claim 1 , wherein the laser intensity distribution is made uniform by passing a laser beam irradiated from at least one direction through a homogenizer . The method for producing a polyester multifilament according to claim 1 or 2, wherein a mirror having a cooling mechanism is used.