JP4729410B2 - Crimpable polyester fiber and method for producing the same - Google Patents

Description

The present invention relates to a crimped polyester fiber, and more particularly, suitable for use in industrial materials, particularly in applications requiring impregnation with a treatment agent such as rubber reinforcement for tire cords, belts and ropes. The present invention relates to a crimpable polyester fiber having high strength while having crimpability and a method for producing the same.
In the present invention, the “crimpable fiber” refers to a fiber having a three-dimensional crimp that the natural fiber has, and the present invention has the characteristics of such a crimp. It is related to the polyester fiber.

  Polyester fibers have excellent balance in mechanical properties and dimensional stability, and can be manufactured stably by melt spinning / drawing and high-speed spinning methods. It is also widely used for industrial materials.

Under such circumstances, there are cases where it is required to impart a three-dimensional structure called a crimp possessed by natural fibers to an essentially straight polyester fiber spun from a die hole.
Various fibers have been conventionally proposed in which three-dimensional crimps are imparted to the fibers in the melt spinning method.

  For example, there is a side-by-side type composite fiber in which two or more kinds of resins having different shrinkages are arranged in a side-by-side type, or a core-sheath type composite fiber in which a core component is decentered and arranged in a sheath component.

  However, these composite fibers have different fiber cross-sectional structures based on different components, so the deformation mechanisms differ greatly in the cross-sectional area direction. Under high loads, the stress applied to each component differs and stress concentration occurs. Since the structure is easy, the strength of the fiber is low. Furthermore, since the fibers use a plurality of resins in a specific combination in the production process, there is a problem that the yarn-making state becomes unstable in addition to an increase in cost. Certainly, there is a fiber whose strength is improved by subjecting the fiber to a special stretching treatment (see Patent Document 1). However, the strength described in the example of Patent Document 1 is at most about 6.7 g / d (5.9 cN / dtex), and it is clear that the fiber is not suitable for industrial materials.

  On the other hand, there is a disclosure of a single component fiber imparted with crimpability. However, in general, the fiber is subjected to a single-sided contact heat treatment with a hot plate or a hot pin heated to the vicinity of the melting point in the spinning process or drawing process to impart a periodic fiber structure change in the fiber axis direction or cross-sectional direction. Thus, the crimping property is expressed. The fibers obtained by such a method are subject to deterioration due to excessive heating, the formation of crystals that inhibit molecular chain orientation, and inevitably thin spots in the fiber axis direction. Then, stress concentration tends to occur in the crimped part (mountain or valley), and the strength becomes extremely low. In order to improve this problem, there is a disclosure of a method for imparting potential crimpability to a fiber by irradiating a laser beam from one side in a melt spinning process (see Patent Document 2).

  The technique of Patent Document 2 solves the problem caused by the fiber shape change as described above, but in the manufacturing method, the molten resin is forcibly cooled from one side, and a very powerful laser from the other side (Example of Patent Document 2). In this case, a structural difference is imparted in the cross-sectional direction by irradiating with 100 to 300 W), and the fiber strength becomes low due to the deterioration caused by heating or the excessive structural difference as described above. In addition, since the intrinsic viscosity of the raw material resins described in the examples is 0.63 dl / g at most and the strength value is at most 5.2 g / d (4.6 cN / dtex), this is also an industry. It is not a fiber that can withstand material use.

  In addition, the inventors have already disclosed a technique for obtaining undrawn yarn by irradiating a discharged fiber with laser light in a melt spinning process (see Patent Document 3).

  However, in this technique, it is a method for producing a so-called flat yarn having a uniform structure in the cross-sectional direction, and it is possible to produce a polyester fiber excellent in stretchability with excellent yarn production and energy saving. It was difficult to impart crimpability.

As described above, there is no technology relating to a crimpable polyester fiber having high strength suitable for industrial material applications while having excellent crimpability.
JP-A-9-228154 (first page, examples) Japanese Patent Publication No.56-11762 (2nd page) JP 2004-324017 A (first page)

  An object of the present invention is to provide a crimpable polyester fiber suitable for industrial material applications, in particular, rubber reinforcement applications such as tire cords, belt applications, rope applications, and other applications that require an impregnation treatment. It is providing the manufacturing method of a shrinkable polyester fiber. In the present invention, the impregnation treatment means a treatment for impregnating a structural material made of fibers with a treatment liquid such as epoxy or RFL in an application that requires adhesion to other materials such as a tire cord. On the other hand, if there is an appropriate gap between the single fibers constituting the structural material, the treatment agent enters more into the structural material, and the structural material becomes stronger. Therefore, in applications requiring such impregnation treatment, it is desired to realize polyester fibers having crimpability in addition to having high strength that is generally essential for industrial material applications.

The polyester fiber of the present invention that achieves the above-described object is a crimped polyester fiber characterized by simultaneously satisfying the following (1) to (3) .

(1) Strength is 8.0 cN / dtex or more (2) Crimp number is 3.0 pieces / 25 mm or more
(3) Toughness is 30 to 60, and the toughness is a value determined by toughness = strength × √elongation.
In the polyester fiber of the present invention, the elastic modulus is more preferably 130 cN / dtex or more.

In addition, the method for producing a polyester fiber of the present invention that achieves the above-described object is to melt and discharge a polyester having an intrinsic viscosity of 0.8 dl / g or more, and cool down from the spinneret surface to 50 mm along the spinning line. Upstream from the start position, the melted and discharged polyester is irradiated with a laser having a strength I (W / cm ² ) in the following range, then cooled and solidified to obtain an undrawn yarn, and then the undrawn yarn. Is a method for producing a crimpable polyester fiber, characterized by drawing and heat-treating under heat.
50 / D ≦ I ≦ 150 / D
D: Base hole diameter (φmm)

  ADVANTAGE OF THE INVENTION According to this invention, the crimpable polyester fiber suitable for the use which requires the impregnation process by processing agents, such as a rubber reinforcement use, such as a tire cord, a belt use, and a rope use, is provided. Moreover, according to this invention, the method of manufacturing the crimpable polyester fiber suitable for this industrial material use is provided.

  Hereinafter, the best mode for carrying out the crimpable polyester fiber and the method for producing the same according to the present invention will be described.

  The polyester referred to in the present invention is a linear polymer having an ester bond in a repeating structure, and is not particularly limited, but is preferably polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, or polyethylene naphthalate, In particular, polyethylene terephthalate is more preferable. The crimpable polyester fiber of the present invention may be copolymerized with other components as long as the effects of the present invention are not impaired. Further, the crimpable polyester fiber of the present invention may contain a small amount of various appropriate additives such as a matting agent, a flame retardant, or a lubricant.

The crimpable polyester fiber of the present invention is a crimpable polyester fiber that satisfies the following (1) to (3) at the same time, and the polyester fiber of the present invention exhibits the effects described below. .
(1) Strength is 8.0 cN / dtex or more (2) Crimp number is 3.0 pieces / 25 mm or more
(3) Toughness is 30 to 60, and the toughness is a value determined by toughness = strength × √elongation.

  That is, in the recent trend of high technology, considering the quality level required as a structural material for industrial materials, the strength is required to be at least 8.0 cN / dtex. Further, in order to satisfy a high level of demand and to enable expansion of applications in industrial materials, it is preferably 10.0 cN / dtex or more. The upper limit is preferably up to 20.0 cN / dtex according to the knowledge of the present inventors, taking into consideration the good productivity and the like.

In recent years, while attention has been paid to the environmental load in the manufacturing process and the disposal process, it is strongly desired to expand the use of polyester fibers in industrial materials, which can be recycled relatively easily and inexpensively. One of the factors that limit the use of polyester fibers in industrial materials is that the impregnation rate of the treatment agent is low because the treatment agent is difficult to enter the structure material when impregnation with the treatment agent is performed. In addition, there is a problem that the adhesiveness is low, and peeling from other materials easily occurs when used. The inventors of the present invention have made extensive studies on this problem, and imparting crimpability to the polyester fiber, thereby forming an appropriate gap between the single fibers when used as a woven fabric. For example, it is used for a tire cord. It has been found that when the impregnation treatment is performed with a treatment agent such as epoxy or RFL, the treatment agent can easily enter the voids, so that the adhesion to rubber is improved. Furthermore, since the treatment agent reinforces the single fiber, the performance as a tire cord is greatly improved. In order to obtain this effect, it is necessary that the single fiber has a number of crimps of at least 3.0 pieces / 25 mm or more. To make this effect more prominent, it is 6.0 pieces / 25 mm or more. It is preferable to do. The upper limit of the number of crimps is preferably 20.0 pieces / 25 mm, which is substantially difficult to manufacture in order to satisfy the above-described strength level at the same time, and 15.0 pieces in order to satisfy the above-described properties at the same time. / 25 mm or less is more preferable. Further, the crimp elongation rate is preferably 40% or more, and more preferably 50% or more. In the present invention, considering the good productivity, the upper limit of the crimp elongation is about 70%. Note that the crimp elongation rate in the present invention is a sample having a circumference of about 1.0 m, and the length under a 0.2 mg / dtex load and the length under a 200 mg / dtex load are measured. This is the value obtained from the formula.
K (%) = {(L ₂ −L ₁ ) / L ₁ } × 100
K: Crimp elongation (%)
L ₁ : Length at the time of 0.2 mg / dtex load (mm),
L ₂ : Length at the time of 200 mg / dtex load (mm),

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 of the fiber over time, resulting in deterioration of mechanical properties and breakage. Deterioration progresses as A fiber having an excellent elastic modulus can bear the stress of elongation and compression by elastic deformation, so that plastic deformation is small and deterioration of the fiber and the structural material can be minimized. Therefore, the elastic modulus of the crimpable polyester of the present invention is preferably 130 cN / dtex or more, and more preferably 150 cN / dtex or more. The upper limit is up to 250 cN / dtex according to the knowledge of the present inventors, considering the good productivity. Furthermore, the 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 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 important that the toughness is 30 or more, and in order to make this characteristic remarkable, it is more preferable to set the toughness to be 35 or more. The upper limit is up to 60 considering good productivity .

The specific manufacturing method of the crimpable polyester fiber of this invention is demonstrated below.
Since the crimpable polyester fiber of the present invention needs to retain mechanical properties suitable for industrial material applications, the higher the intrinsic viscosity of the polyester resin used, the more preferable, at least 0.8 dl / g or more, It is important to use those having 1.0 dl / g or more. In order to further increase the strength, the intrinsic viscosity of the resin is more preferably 1.2 dl / g or more. The upper limit is not particularly limited, but is about 5.0 dl / g considering the spinning limit in the melt spinning process.

  In the melt spinning process, a molten resin melted and measured by a conventional method is melted and discharged from a spinneret. In addition, the nozzle | cap | die hole in this invention is an exit diameter of the discharge hole pierced by the nozzle | cap | die, and a deformed hole may be sufficient as it.

  The resin melted and discharged from the spinneret is irradiated with laser light between the spinneret surface and 50 mm upstream of the cooling start position. In the present invention, the spinneret surface means a position where the discharged resin has a free surface and can be extended and deformed, and the laser beam irradiation position needs to be between 50 mm from the spinneret surface. When the laser beam irradiation reaches a downstream position more than 50 mm from the spinneret, the resin temperature generally decreases to 250 ° C. or lower, making it difficult to set the resin temperature at the laser beam irradiation position to the melting point or higher. This should be avoided because the effect of laser irradiation described later is greatly reduced.

  The laser light in the present invention is monochromatic light, a parallel light beam, and a coherent light beam. The type of laser is not particularly limited, but it is preferable to use a carbon dioxide laser because a large output can be obtained and it is inexpensive.

  The cooling in the present invention means that the cooling air is blown from one side or the periphery by a cooling air generator such as a quench chamber to forcibly reduce the resin temperature. In the manufacturing method of the present invention, this cooling is performed. The laser beam is irradiated to the molten resin upstream of the starting position. In the present invention, the molten resin is cooled and solidified by being actively cooled after receiving the laser irradiation. In addition, if cooling is performed at the laser irradiation position in the present invention, the melt resin temperature is greatly deteriorated and the molten resin temperature is greatly reduced. It falls and it becomes difficult to obtain the crimpable polyester fiber of this invention.

The intensity I (W / cm ² ) of the laser applied to the molten resin needs to satisfy the following range.
50 / D ≦ I ≦ 150 / D
D: Base hole diameter (φmm)

  If the laser intensity is lower than this range, the structural difference in the cross-sectional direction cannot be obtained, so that crimpability is not imparted. If the laser intensity is higher than this range, the laser intensity is excessive and the intensity decreases. At the same time, the yarn forming property is extremely deteriorated. Therefore, the laser intensity is preferably 130 / D or less in order to obtain the crimpable polyester of the present invention with good yarn forming properties, and 110 / D or less in order to balance the crimpability and strength. Is more preferable.

  The cross-sectional shape of the laser light can be changed to a circle or a square by using a lens optical system, and the laser irradiation spot area can be adjusted by a beam expander. 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 order to increase the strength of the obtained fiber, the diameter of the die hole is preferably φ0.6 mm or less, and more preferably φ0.3 mm or less for the purpose of maintaining strength.

  The laser-irradiated resin is cooled and solidified, and then taken out to form an undrawn yarn. The take-up method is not particularly limited, and any method such as a so-called two-step method or a direct drawing method can be employed. In order to maintain the crimpability and strength of the polyester fiber of the present invention, it is necessary to heat-treat after stretching under heating. As a heating method in the drawing process, it is preferable to take any one of the heating roller, the hot plate, the hot pin, and the like in consideration of the obtained yarn characteristics, mechanical configuration, workability, and the like.

  As a stretching method, for example, there is a method of stretching between a pair of rollers having different rotation speeds. In order to develop the strength, it is necessary to stably perform the high magnification stretching, and it is preferable that the treatment temperature in the stretching step can be changed stepwise, so that the number of stretching steps is preferably two or more.

  It is important to determine the draw ratio of each stage so as to satisfy the above-described requirements (1) and (2) of the crimpable polyester fiber according to the present invention. According to the knowledge of the present inventors, In a normal case, although not particularly limited, in order to obtain a crimped polyester fiber having a total magnification of 4.0 to 7.0 times, in particular, good strength and crimpability, The total magnification is preferably 5.0 to 6.0 times, and if higher strength is required depending on the application, the second stage draw ratio is 1.3 to 1.8. It is good to make it about twice.

  The heat treatment is preferably performed before the final cooling step (for example, a cold roll), and the heat treatment temperature is preferably (melting point of the resin used −80) ° C. or higher and (melting point of the resin used −20) ° C. or lower. By performing the heat setting process, the crimped structure is fixed.

  The crimpable polyester fiber of the present invention is an unprecedented polyester fiber having a high strength of not less than 8.0 cN / dtex while having crimpability, and is produced by melt spinning of the present inventors. As a result of the study on the fibers, it has been found that the high strength is achieved by controlling the entanglement structure of the molecular chains. The undrawn yarn of which the structure is controlled has improved homogeneity of the entangled state of the molecular chain, and an excellent fiber structure is formed by aligning and fixing the structure, and the strength is 8.0 cN / dtex or more. It becomes a fiber having high strength. The entangled structure of molecular chains in the present invention means a network structure formed by entanglement of molecular chains, and is generally fixed at (melting point−20) ° C. In addition, the entangled structure once fixed does not change, and this structure stretches while maintaining the network in the drawing process, so that the final fiber structure is greatly affected. In other words, in order to obtain a fiber having high strength, it is necessary to homogenize the molecular chain entanglement structure and improve the substantial molecular chain orientation, and the present inventors utilize the decrease in the melt viscosity of the resin by laser light irradiation. This was achieved by promoting thinning at high temperatures.

On the other hand, for the expression of crimping, it is important to set the laser intensity I (W / cm ² ) within a specific range. Since the laser beam is radiant energy, the resin can generally be heated instantaneously and almost uniformly in the cross-section direction of the molten resin, but the molten resin has a large diameter and a high temperature within 50 mm from the spinneret. When a certain resin is irradiated with a laser with an intensity of 50 / D or more, the absorption on the laser irradiation side is large, the temperature on the laser irradiation side increases first, and an entanglement structure difference of molecular chains is produced in the fiber cross-sectional direction. It is possible to impart latent crimpability to the single fiber. The undrawn yarn that has been subjected to such a treatment is subjected to a heat setting step after the drawing step, thereby exhibiting crimping properties associated with the molecular chain entanglement structure change. Note that crimpability becomes noticeable by increasing the laser intensity. However, if it is higher than 150 / D, the decrease in melt viscosity becomes excessive. The inner diameter of the molten resin is reduced. As a result, the heating effect decreases, but for this reason, the start point of the thinning shifts downstream, and the diameter of the molten resin becomes thick again. By repeating this, since it becomes a fiber having a variation in diameter in the fiber axis direction, it tends to become prominent as crimpability, in addition to the difficulty in satisfying the scope of the present invention, This is not preferable because the yarn-making property is significantly deteriorated.

  As described above, the present inventors diligently studied the laser light irradiation conditions in the vicinity of the spinneret, and as a result, the effect of controlling the molecular chain entanglement structure described above was changed stepwise in the cross-sectional direction of the single fiber. It has been found that potential crimpability can be imparted at the drawn yarn stage. Further, it was discovered that the crimpability can be made remarkable by stretching and heat-setting it under heating, and a polyester fiber having high strength while having crimpability like the crimpable polyester fiber of the present invention is obtained. Succeeded in getting.

  The combination of the mechanisms as described above makes it possible to achieve both of the characteristics that cannot be obtained by the prior art as the crimped polyester fiber of the present invention has.

  In addition, although the fiber with the controlled molecular chain entanglement structure obtained by the technique of the present invention has excellent characteristics, when the structural process by orientation crystallization is performed in the spinning process, the strength is expressed by stretching. Therefore, the take-up speed of the undrawn yarn is preferably set to a speed at which orientation crystallization does not substantially occur, and specifically, less than 1000 m / min. More preferably, it is 700 m / min or less. The lower limit of the take-up speed is preferably 300 m / min in view of productivity.

  The polyester fiber of the present invention may be multifilament or monofilament. In the case of a multifilament, it is suitable as a fiber for industrial materials that the fineness ranges from 10 dtex to 10000 dtex, the number of filaments ranges from 2 to 5000, and the single yarn fineness ranges from 0.1 dtex to 100 dtex.

  When the crimpable polyester fiber of the present invention is used as a fiber for reinforcing rubber of tires or the like, usually, after obtaining a multifilament, a lower twist, an upper twist is imparted to form a twisted cord, and if necessary, Then, weaving and / or applying an epoxy processing solution, drying, applying an RFL processing solution, and drying to obtain a dip cord (woven fabric). The crimped polyester fiber of the present invention has a high permeability to the cord of epoxy or RFL treatment liquid and can be a cord excellent in adhesiveness with rubber. A rubber product reinforced by this cord is durable. Excellent in strength, strength and elastic modulus.

  In addition to rubber reinforcing fibers such as tires, hoses, and belts, the crimpable polyester fiber of the present invention includes resin reinforcing fibers, nets such as fishing nets, land nets, ropes, belts such as seat belts and slings, air It can be widely used for bags, fabrics such as rubber and resin coating fabrics, and the like.

  Examples and Comparative Examples are shown below, and the present invention will be described specifically and in detail. However, the present invention is not limited by the following examples. In addition, the physical-property value in an Example and a comparative example is measured with the following method.

  In any measurement, in the case of obtaining a numerical value, unless otherwise specified, n is 20 and is averaged. The n number may be further increased depending on how data is output.

A. Intrinsic viscosity (dl / g)
Orthochlorophenol was measured at 25 ° C. In this example, Shodex GPC-101 manufactured by Showa Denko Co., Ltd. was used and measured with an eluent HFIP, a column HFIP-806M × 2, a detector RI, and a flow rate of 1.0 mL / min. Conversion was performed using terephthalate.

B. Fineness (dtex)
The fineness was calculated from the weight of the test fiber length 100 m using a measuring instrument (HD-3) manufactured by Daiei Kagaku Seiki Co., Ltd.

C. Strength, elongation, elastic modulus and toughness Strength, elongation, and elastic modulus were measured using an autograph manufactured by Shimadzu Corporation at an initial sample of 50 mm (unstretched fiber), 100 mm (stretched fiber), and a tensile rate of 100% / min. The stress-strain curve was measured and determined.

The toughness was determined from the values of strength (cN / dtex) and elongation (%) by toughness = strength × (elongation) ^1/2 .

D. Laser intensity (W / cm ² )
With the resin not running, a laser power meter was installed at the running position of the fiber (discharge resin) to measure the laser irradiation energy, and this was divided by the cross-sectional area obtained from the fiber diameter at the time of irradiation.

E. Number of crimps (pieces / 25mm)
It was determined in accordance with JIS L 1015 (1999) “Test Method for Chemical Fiber Staples”, 8.12.1 Crimp Number Measurement Method. In addition, the JIS is an average of data of n number of 20 pieces, and rounds a numerical value to the last one. If the number of crimps as a result of the rounding is 2.5 pieces / 25 mm or more, This corresponds to the number of crimps described above of 3.0 / 25 mm or more.

Example 1
Polyethylene terephthalate (inherent viscosity: 1.0 dl / g) was melted by a biaxial extruder and discharged at a spinning temperature of 300 ° C. and a spinneret (hole diameter φ0.6 mm, number of holes 1) at a single hole discharge rate of 3.0 g / min. . A carbon dioxide laser with a laser intensity of 170 W / cm ² was irradiated 10 mm downstream from the spinneret surface, and after cooling and solidification, the yarn was taken out at a spinning speed of 500 m / 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 fiber.

Comparative Example 1
Except that the intrinsic viscosity of the resin was 0.6 dl / g and the spinning temperature was 290 ° 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 fiber.

Example 2
Except that the intrinsic viscosity of the resin used was 0.8 dl / g, 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 fiber.

Example 3
Except that the intrinsic viscosity of the resin used was 1.2 dl / g and the spinning temperature was 320 ° 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 fiber.

  As the intrinsic viscosity of the resin used increases, the polyester fiber of the present invention having high strength while having crimpability is obtained. However, in Comparative Example 1 where the intrinsic viscosity is out of the range, it has crimpability but has low strength and does not satisfy the scope of the present invention.

Example 4
Except that the laser irradiation position was set 40 mm downstream from the spinneret, 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 fiber.

Comparative Example 2
Except that the irradiation position was set to 100 mm, 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 fiber.

  As the laser irradiation position shifts downstream, the effect of laser irradiation decreases. In the case of Comparative Example 2, which is outside the scope of the present invention, the effect of laser light irradiation is not observed, and a relatively high strength is obtained, but the crimpability is hardly maintained.

Comparative Example 3
Yarn production was performed in the same manner as in Example 1 except that laser light having a laser intensity of 4000 W / cm ² was irradiated on one side at a position 200 mm downstream from the spinneret surface to obtain a drawn yarn. Table 1 shows the physical properties of the obtained fiber.

  When the laser irradiation position is set downstream and the laser intensity is increased, the structural difference in the cross-sectional direction is excessive, and high crimpability is maintained, but the intensity is significantly reduced. Furthermore, since the stability of the spinning process is lowered, it is not possible to carry out high magnification drawing.

Comparative Example 4
Except that the laser intensity was set to 60 W / cm ² , 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 fiber.

Comparative Example 5
Except that the laser intensity was set to 300 W / cm ² , 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 fiber.

  As can be seen from Table 1, when the laser irradiation intensity is out of the range of the present invention, the crimping property according to the present invention in which the intensity is 8.0 cN / dtex or more and the number of crimps is 3/25 mm or more. There is no satisfaction with polyester fiber.

  From the above, outside of the condition range specified by the method of the present invention, the expression of crimpability and strength retention are not compatible.

  On the other hand, the crimpable polyester fiber of the present invention has moderate crimpability and is excellent in both strength and elastic modulus, realizing a polyester fiber that could not be obtained by the prior art. I understand that.

Claims (3)

A crimpable polyester fiber characterized by satisfying the following (1) to (3) in the polyester fiber.
(1) Strength is 8.0 cN / dtex or more (2) Crimp number is 3.0 pieces / 25 mm or more
(3) Toughness is 30 to 60, and the toughness is a value determined by toughness = strength × √elongation.   The crimpable polyester fiber according to claim 1, wherein the elastic modulus is 130 cN / dtex or more. A polyester having an intrinsic viscosity of 0.8 dl / g or more is melted and discharged, and the strength I (with respect to the melted and discharged polyester is 50 mm along the spinning line from the spinneret surface and upstream from the cooling start position. W / cm ² ) irradiation with a laser having the following range, followed by cooling and solidification to obtain an undrawn yarn, and subsequently drawing and heat-treating the undrawn yarn under heating Manufacturing method.
50 / D ≦ I ≦ 150 / D
D: Base hole diameter (φmm)