JP4826416B2 - Core-sheath type composite fiber - Google Patents

Description

  The present invention relates to a core-sheath type composite fiber that is excellent in high strength, high elastic modulus, and wear resistance and that expresses uniform surface characteristics in all directions. , General industrial materials, especially ropes, rubber reinforcements, geotextiles, FRP applications, computer ribbons, printed circuit board fabrics, air bags, bag filters, fishing nets and other marine products, screen rods, etc. Since it is uniform in thickness, it exhibits uniform characteristics in all directions in the fiber cross section of a single yarn. Therefore, the fiber is particularly suitable for monofilaments used for filters, meshes for screen wrinkles, and the like.

  Liquid crystal polyester fibers are known to have high strength and high elastic modulus because molecular chains are highly oriented in the fiber axis direction. However, since a weak intermolecular force acts only in a direction perpendicular to the fiber axis, fibrils are easily generated by friction, causing a problem such as a decrease in fiber strength leading to breakage. Further, since kink bands due to buckling tend to occur and tend to localize, the fatigue resistance is poor.

Therefore, for the purpose of improving these drawbacks, a core-sheath type composite fiber in which the core component is liquid crystalline polyester and the sheath component is polyphenylene sulfide has been proposed (see Patent Document 1). In addition, the core component consists of a liquid crystal polyester as the core component and a polymer alloy consisting of a liquid crystal polyester and a flexible polymer as the core component as an improvement in wear resistance and fatigue resistance by suppressing peeling and fibrillation at the core / sheath component interface. A sheath type composite fiber (see Patent Documents 2 and 3) has been proposed. Furthermore, as the core-sheath interface peeling was suppressed, the core-sheath type composite fiber (see Patent Document 4) in which fluctuations were formed at the core-sheath interface, improved adhesion of the core-sheath component, and improved abrasion resistance of the yarn surface Is a polymer blend composed of a flexible polymer and a C component having a high affinity for the liquid crystalline polyester as the core component, and the C component concentration is high on the core component side and the yarn surface layer side. A lowered core-sheath type composite fiber (see Patent Document 5) has been proposed.
JP-A-3-220340 (FIG. 2) Japanese Patent Laid-Open No. 5-230715 (FIG. 2) JP-A-8-260249 (FIG. 1) Japanese Patent Laid-Open No. 9-310245 (FIG. 2) JP 2000-034621 A (page 2, right section 4)

  As described above, it is a fact that the fibrillation is suppressed and the wear resistance is improved by coating the periphery of the liquid crystalline polyester as a core-sheath type composite fiber with a polymer that is difficult to fibrillate.

  However, when making a composite fiber in which liquid crystal polyester is arranged on such a core component, the melt viscosity of liquid crystal polyester is easily affected by shear stress, and the thermal characteristics of the polymer are often different from those of a flexible polymer. When the liquid crystal polyester and the flexible polymer merge in the spinneret and flow as a composite flow, the flow deformation of each component becomes unstable, the fiber structure tends to be biased, and the sheath component thickness is continuously increased. It was difficult to form uniformly.

  In addition, in the thinning deformation process after spinning, the deformation of the liquid crystalline polyester proceeds at a stretch at a high temperature, which increases the unevenness of the thickness of the sheath component in the supercooled and melted state. It was difficult to make it uniform.

  Such variation in sheath component thickness leads to uneven thickness of the fiber, which is an important problem especially for monofilament applications. Reflected by uneven application of ink, the thickness of the sheath component necessary to improve quality and wear durability must be increased unnecessarily, and the improvement in strength is sacrificed. Had a problem.

  Therefore, as a result of intensive studies on liquid crystal polyester composite fibers having a uniform sheath component thickness, the present invention has been achieved.

The present invention, unrealized 50 wt% or more of the liquid crystal polyester in the core component, and a composite ratio Rs of the liquid crystal polyester in the sheath component is in the range of less than 15 wt% to 50 wt%, the core component and sheath component are both liquid crystal polyester the a including core-sheath type composite fibers, the thickness of the sheath component in the fiber cross-section, characterized in that the relationship between the maximum thickness (Tmax) and the minimum value (Tmin) is, satisfies Tmax / Tmin ≦ 2.0 And a core-sheath type composite fiber.

  The present invention provides a core-sheath type composite fiber having excellent abrasion resistance while having high strength and high elastic modulus of a melt liquid crystal forming polyester, and industrial materials such as screen wrinkles and filters as monofilaments As a multifilament, it can be widely used in the fields of civil engineering / building materials, sports applications, protective clothing, rubber reinforcing materials, electric wire reinforcing materials, acoustic materials, general clothing and the like.

  The liquid crystal polyester in the core-sheath composite fiber of the present invention refers to a polymer that exhibits optical anisotropy (liquid crystallinity) when heated and melted. This characteristic can be confirmed, for example, by placing a sample made of liquid crystal polyester on a hot stage, heating and heating in a nitrogen atmosphere, and observing the transmitted light of the sample under polarized light.

  A conventionally well-known method can be employ | adopted for the polymerization prescription of liquid crystal polyester used for this invention.

  Examples of the liquid crystal polyester used in the present invention include a. A polymer of aromatic oxycarboxylic acid, b. Polymer of aromatic dicarboxylic acid and aromatic diol, aliphatic diol, c. and a copolymer of a and b.

  Here, examples of the aromatic oxycarboxylic acid include hydroxybenzoic acid, hydroxynaphthoic acid and the like, and alkyl, alkoxy and halogen substituted products of the above aromatic oxycarboxylic acid.

  Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, diphenyldicarboxylic acid, naphthalene dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylethanedicarboxylic acid, and the like, or alkyl, alkoxy, Examples include halogen substitution products.

  Furthermore, examples of the aromatic diol include hydroquinone, resorcin, dioxydiphenyl, naphthalene diol, and the like, and alkyl, alkoxy, and halogen substituted products of the above aromatic diol. Examples of the aliphatic diol include ethylene glycol, propylene glycol, Examples include butanediol and neopentyl glycol.

  Preferred examples of the liquid crystalline polyester used in the present invention include a copolymer of a p-hydroxybenzoic acid component and an ethylene terephthalate component, a p-hydroxybenzoic acid component, a 4,4′-dihydroxybiphenyl component, and a terephthalic acid component or A copolymer of an isophthalic acid component, a copolymer of a p-hydroxybenzoic acid component and a 6-hydroxy 2-naphthoic acid component, a p-hydroxybenzoic acid component and a 6-hydroxy 2-naphthoic acid component, Examples include a copolymer of a hydroquinone component and a terephthalic acid component.

  About the combination of the constituent components of the liquid crystal polyester used in the present invention, the combination ratio and the polymer molecular chain end group, etc., because it affects the stability during storage under heat, thermal decomposability, affinity with other polymers, etc. It is preferable to make various selections in consideration of the intended use and the manufacturing process.

  The melting point of the liquid crystalline polyester used in the present invention is preferably in the range of 220 to 380 ° C., more preferably 250 to 350 ° C. so as not to cause processing problems in spinning, solid phase polymerization and the like.

  The core-sheath type composite fiber of the present invention is characterized in that the core component contains 50% by weight or more of liquid crystal polyester, and by doing so, the liquid crystal polyester has high strength and high elastic modulus. be able to. Moreover, a flexible polymer can be used as materials other than liquid crystal polyester of the core component of the core-sheath type composite fiber of this invention.

  The sheath component of the core-sheath composite fiber of the present invention can contain liquid crystal polyester and a flexible polymer in an arbitrary ratio, but in order to improve the wear resistance, it may contain a flexible polymer. preferable. In addition, by adopting a structure containing liquid crystal polyester also in the sheath component, an adhesion portion between the liquid crystal polyesters can be formed at the core-sheath interface portion. This is preferable because it can be increased and leads to higher strength. Further, when both the core component and the sheath component contain a liquid crystal polyester and a flexible polymer, it is preferable because the adhesion at the core-sheath interface is improved and the wear resistance is improved, and the dispersion component in the sheath component is a liquid crystal polyester. Since the wear resistance is further improved, it is preferably used.

  Furthermore, when both the core component and the sheath component of the core-sheath composite fiber of the present invention contain a liquid crystal polyester and a flexible polymer, it is preferable that the dispersed component of both components is a liquid crystal polyester. By adopting such a structure, the interface between the flexible polymers in the vicinity of the boundary between the core component and the sheath component is increased, so that the adhesiveness of the core-sheath interface can be further improved, and handling properties in various post-processing Can provide excellent products.

  Further, in the case where the dispersion component is a liquid crystal polyester, in the cross section of the single yarn, the fiber diameter obtained from the circumscribed circle of the fiber is (R), and similarly in one dispersion component in the fiber When the diameter obtained from the circumscribed circle of the dispersion component is (r), it is preferable that all dispersion components satisfy r / R ≦ 0.3, and satisfy r / R ≦ 0.2. It is more preferable that In order to obtain high strength and high elastic modulus, the minimum dispersion component in the core component preferably satisfies r / R ≧ 0.001.

  In addition, about the ratio of liquid crystalline polyester, the photograph which imaged the fiber cross section with the magnification of 5000 times with the transmission electron microscope (TEM (H-800 type | mold) by Hitachi, Ltd.), for example, image processing software made by Mitani Corporation (Winroof) can be used for confirmation.

  The bendable polymer used for the core-sheath type composite fiber of the present invention may be one kind of bendable polymer or a polymer alloy composed of two or more kinds of bendable polymers.

  The flexible polymer used for the core-sheath type composite fiber of the present invention is, for example, a vinyl polymer such as polyester, polyolefin or polystyrene, polycarbonate, polyamide, polyimide, polyphenylene sulfide, polyphenylene oxide, polysulfone, aromatic polyketone, aliphatic polyketone, Semi-aromatic polyester amide, polyether ether ketone, fluororesin and the like can be mentioned. Among these flexible polymers, polyphenylene sulfide and polyether ether ketone are preferable from the viewpoint of imparting characteristics such as heat resistance and solvent resistance. From the viewpoint of adhesiveness with rubber or the like, polyamides represented by nylon 6, nylon 66, nylon 46, nylon 6T, nylon 9T and the like are preferable. Further, from the viewpoint of wear resistance in various processing, preferably, polyesters typified by polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycyclohexanedimethanol terephthalate, polyester 99M and the like can be mentioned.

  The flexible polymer used in the core-sheath type composite fiber of the present invention has high affinity with liquid crystal polyester, and is stable even when spinning at a temperature matched to liquid crystal polyester. In various post-processing such as solid phase polymerization after spinning, It is preferable to select a polymer having excellent processability, and the melting point (Tm) of the polymer is preferably in the range of the melting point ± 30 ° C. of the liquid crystal polyester.

  The bendable polymer used in the core-sheath type composite fiber of the present invention may contain other copolymer components in a proportion of 20 mol%, more preferably 10 mol% or less. For example, the compound copolymerizable with polyamide may include, but is not limited to, sodium acrylate, N-vinylpyrrolidone, acrylic acid, methacrylic acid, vinyl alcohol, and a crosslinked polyethylene oxide polymer. . The compounds copolymerizable with polyester include terephthalic acid, isophthalic acid, phthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, benzophenone dicarboxylic acid, and phenylindane dicarboxylic acid. , Oxalic acid, succinic acid, adipic acid, dimer acid, sebacic acid, cyclohexanedicarboxylic acid and other dicarboxylic acids, glycol component ethylene glycol, diethylene glycol, butanediol, neopentyl glycol, cyclohexanedimethanol, polyethylene glycol, polypropylene glycol, etc. It can be mentioned, but is not limited to these.

  The liquid crystalline polyester and the flexible polymer used in the present invention include various metal oxides, inorganic substances such as kaolin and silica, colorants, matting agents, flame retardants and antioxidants within the range not impairing the effects of the present invention. A small amount of various additives such as ultraviolet absorbers, infrared absorbers, crystal nucleating agents, fluorescent brighteners, end group capping agents and compatibilizers may be contained.

  In the core-sheath type composite fiber of the present invention, the relationship between the maximum value (Tmax) and the minimum value (Tmin) of the thickness of the sheath component in the single yarn cross section satisfies Tmax / Tmin ≦ 2.0. By having Tmax / Tmin ≦ 2.0, the characteristics of the sheath component can be uniformly expressed in all directions of the fiber cross section.

  The relationship of Tmax / Tmin is preferably 1.75 or less, more preferably 1.3 or less.

  About the maximum value (Tmax) and the minimum value (Tmin) of the thickness of a sheath component, it calculates | requires from the cross-sectional whole image of the single yarn image | photographed, for example with the transmission electron microscope (For example, TEM (H-800 type | mold made by Hitachi, Ltd.)). . In this case, the cross-section of the fiber is a slice of 0.1 μm of a sample embedded by a normal method, using a sample with relatively little wrinkles and cross-sectional deformation, observation is performed with a single yarn, The n number is 2, and the average value of Tmax / Tmin of each single yarn is Tmax / Tmin of the sample.

  The fiber cross-sectional shape of the core-sheath type composite fiber of the present invention may be any shape as long as Tmax / Tmin ≦ 2.0 is satisfied, but the improvement in wear resistance or the opening of the monofilament woven fabric From the viewpoint of uniformity, a core-sheath type composite fiber having a round cross section and concentric circles is preferable.

  About the core-sheath type composite fiber of this invention, it is preferable that the relationship between single yarn fineness D (dtex) and the minimum value Tmin (micrometer) of sheath component thickness satisfies the following formula.

Formula) Tmin ≧ 1 / 3√D
By satisfying this formula, the sheath component thickness is in an appropriate range with respect to the single yarn fineness, and excellent wear resistance can be exhibited at any fineness.

  In the core-sheath type composite fiber of the present invention, when the core component and the sheath component are both polymer alloys composed of liquid crystal polyester and a flexible polymer, the composite ratio Rc of the liquid crystal polyester in the core component is preferably less than 90% by weight. . By setting the composite ratio Rc of the liquid crystal polyester in the core component to less than 90% by weight, the amount of the flexible polymer existing at the core-sheath interface portion increases, and thus the adhesive force at the core-sheath interface is improved. The composite ratio Rc of the liquid crystal polyester in the core component is more preferably in the range of 60 to 75% by weight.

The composite ratio Rs (wt%) of the liquid crystal polyester in the sheath component, area by der less than 15 wt% to 50 wt%. By making the composite ratio Rs of the liquid crystal polyester in the sheath component 15% by weight or more , the strength can be increased. Further, by setting the composite ratio Rs of the liquid crystal polyester in the sheath component to less than 50% by weight, a large amount of flexible polymer can be present on the fiber surface, so that the abrasion resistance of the fiber surface is increased and fluff is generated. Is suppressed. The composite ratio Rs of the liquid crystal polyester in the sheath component is more preferably in the range of 15 to 40% by weight, and still more preferably in the range of 20 to 35% by weight.

  In this case, the composite ratio of the liquid crystalline polyester in the core component and the sheath component is, for example, an image manufactured by Mitani Corporation for a photograph of a fiber cross section taken with a transmission electron microscope (TEM (H-800 type manufactured by Hitachi, Ltd.)). This can be confirmed using processing software (Winroof).

  The core-sheath type composite fiber of the present invention has high strength and high elastic modulus, which are the characteristics of liquid crystal polyester, and the tensile strength of the fiber is preferably 10 cN / dtex or more, more preferably 14 cN / dtex. That's it. In addition, in order to ensure sufficient dimensional stability and durability of the product in various applications, the elastic modulus is preferably 300 cN / dtex or more, more preferably 350 cN / dtex or more.

  Although an example about the manufacturing method of the core sheath type composite fiber of the present invention is shown below, the present invention is not limited at all by this.

  The polymer of the core component and the sheath component is supplied to the composite spinning apparatus by a known method. Thereafter, the polymer of each component is weighed, filtered, and led to a core-sheath type compound spinneret. When the polymer to be supplied is a mixture, the mixture is prepared before melt spinning or simultaneously with melt spinning. Examples thereof include a single-screw kneader, a twin-screw kneader, various kneaders, and a static kneader. Can also be used.

  The core-sheath type composite cap is an important part for controlling the thickness of the core-sheath type composite fiber sheath component of the present invention within the range of the present invention. Liquid crystalline polyester is a polymer whose melt viscosity is highly dependent on the shear rate, and when joining with a flexible polymer in the molten state, the polymer flow tends to be biased or turbulent, or its time variation tends to occur. There was a limit. The core-sheath composite spinneret for obtaining the core-sheath composite fiber of the present invention will be described with reference to FIG. 1 using a core-sheath composite spinneret having a special structure described below.

The core-sheath composite spinneret for obtaining the core-sheath-type conjugate fiber of the present invention includes, first, a core component restricting portion 1, a stabilizing channel 2, a core-sheath component merging portion 3, a composite flow inflow hole 4, and a discharge hole. 5 is arranged on a straight line, and the core component polymer flows on this axis. However, after the core-sheath component merging portion 3, the sheath component polymer is coated with the core component polymer. If necessary, a core component inflow hole 6 is provided on the upstream side of the core component restricting portion 1. Second, the flow path cross-sectional area of the core component diaphragm portion 1, 0.2 mm ² or less, preferably 0.15 mm ² or less, more preferably a 0.10 mm ² or less, thereby weighing the core component polymer. In this case, the lower limit of the cross-sectional area is 0.01 mm ² . Third, the length of the stabilization flow path 2 is 5 mm or more, and if necessary, near the end of the stabilization flow path 2, the sectional area is again 0.2 mm ² or more and 2.0 mm ² or less. (Referred to as the core component second aperture 7). The core component polymer passes through the core component restricting portion 1 and the stabilizing flow path 2 and can merge with the sheath component in a state where the shear strain is small while measuring, and suppresses fluctuations in the sheath thickness. On the other hand, when the cross-sectional area of the second throttle portion 7 is less than 0.2 mm ² , shear strain is added to the stabilized core component flow, so that the sheath thickness variation becomes large. For this purpose, the cross-sectional area of the second throttle portion 7 is preferably 0.3 mm ² or more.

The core-sheath composite spinneret for obtaining the core-sheath-type conjugate fiber of the present invention fourthly arranges the sheath component constricted portion 8 upstream of the core-sheath component joining portion 3 for the sheath component. The channel cross-sectional area of the sheath component aperture section 8, 0.2 mm ² or less, preferably 0.15 mm ² or less, more preferably a 0.10 mm ² or less, thereby weighing the sheath component polymer. In this case, the lower limit of the cross-sectional area is 0.01 mm ² . A plurality of sheath component restricting portions 8 are provided on concentric circles centering on the flow axis of the core component to make the coating thickness of the sheath component polymer uniform. Fifth, the sheath-component polymer is joined at the core-sheath component merging portion 3 so as to cover the entire circumference of the core component. By passing through the sheath component restricting portion 8 and the core-sheath component merging portion 3, the sheath component polymer can be merged with the core component at a low flow rate while being measured, and suppresses variation in the sheath thickness.

  The core-sheath type composite fiber of the present invention already has sufficient strength and elastic modulus just by spinning because it contains liquid crystalline polyester, but the performance can be further improved by solid phase polymerization. The solid phase polymerization can be performed in an inert gas atmosphere such as nitrogen, an active gas atmosphere containing oxygen such as air, or under reduced pressure. The atmosphere of solid phase polymerization is preferably a low-humidity gas having a dew point of −40 ° C. or lower. The solid-state polymerization conditions are as follows: a polymer having the lowest melting point of the polymer exposed on the fiber surface is used as a reference component, and the solid-phase polymerization is performed at a temperature not exceeding the melting point of the reference component from a temperature lower by about 40 ° C. Preferably it is done. At this time, in order to prevent inter-fiber fusion, the solid phase polymerization temperature is preferably about 5 ° C. lower than the melting point of the reference component. The starting temperature of the solid phase polymerization can be any temperature as long as it is not higher than the temperature at which the solid phase polymerization is performed. Furthermore, the solid phase polymerization time is several minutes to several tens of hours depending on the target performance.

  Regarding the temperature increase of solid phase polymerization, in order to prevent fusion between fibers due to a rapid temperature increase, it is preferable to increase the temperature stepwise, and the temperature does not exceed the crystallization temperature of the reference component for several minutes to several hours. A stage for promoting crystallization, such as a treatment, may be provided.

Here, the crystallization temperature is measured under a temperature increase condition of 16 ° C./min from room temperature in a differential calorimetry performed by a differential scanning calorimeter (DSC) manufactured by PerkinElmer Co., Ltd. using a spinning yarn as a sample. It refers to the exothermic peak temperature (Tc ₁ ) observed at the time.

  In the solid phase polymerization, various additives may be added to promote the solid phase polymerization of the liquid crystalline polyester.

Supply of heat during solid-phase polymerization uses a method using a medium such as liquid and gas, a method using radiation by a heating plate, an infrared heater, etc., a method of making contact with a heating roller, a heating plate, etc., a high frequency, etc. Can be used. The solid phase polymerization is performed under tension or no tension depending on the purpose, and the solid phase polymerization can be performed in a drum shape, a cake shape, a tow shape (for example, on a metal net), or continuously between rollers. It can also be processed as a yarn, and can also be subjected to solid phase polymerization after forming a fiber molded body such as a fabric or woven or knitted fabric.
The core-sheath type composite fiber of the present invention has excellent wear resistance only by performing solid phase polymerization, but in order to further improve the wear resistance, after performing solid phase polymerization, It is preferable to perform a high-temperature short-time heat treatment in which the yarn is melted in a non-contact manner in a temperature atmosphere of a melting point + 20 ° C. or more and a time of 0.001 seconds to 5 seconds. By setting the melting point of the reference component to 20 ° C. or higher, the effect of heat treatment is likely to occur in a short time, so that the heat treatment can be performed efficiently, such as reducing the influence on the strength of the liquid crystal polyester. The heat treatment temperature may be within a general heater temperature control range, preferably in the range of melting point + 20 ° C. to melting point + 500 ° C., more preferably in the range of melting point + 30 ° C. to melting point + 300 ° C. The heat treatment time is preferably 0.001 seconds or more and 5 seconds or less. By setting the heat treatment time within this time range, it is possible to prevent the fibers from being blown while maintaining efficient heat treatment. The heat treatment time is preferably 0.005 seconds to 2 seconds, more preferably 0.01 seconds to 1 second.
Further, non-contact heat treatment is performed in order to prevent wear due to contact with a guide or the like during the heat treatment step and to perform uniform heat treatment. Moreover, as a preferable heat source, a slit heater using a general plate heater, laser heating, or the like can be used.

  By performing a high-temperature and short-time heat treatment, a fiber having a characteristic that the crystallization temperature can be confirmed by differential scanning calorimetry (DSC) measurement even for a yarn after solid-phase polymerization. In this case, heat treatment is preferably performed so that the crystallization heat amount ΔHc is 3 J / g or more.

  The form of the core-sheath type composite fiber of the present invention can be either filament or cut fiber, but in order to fully exhibit the properties of the fiber, it is preferably filament, particularly monofilament.

  The core-sheath type composite fiber of the present invention retains the characteristics of high strength and high elastic modulus, and has remarkably improved fibrillation resistance, wear resistance, and fatigue resistance. Widely used in the fields of building materials, sports applications, protective clothing, rubber reinforcement materials, electrical materials (especially as tension members), acoustic materials, and general clothing. Effective applications include screen kites, computer ribbons, printed circuit board fabrics, paper canvases, airbags, airships, dome fabrics, rider suits, fishing lines, various lines (yachts, paragliders, balloons, kites) Thread), blind cords, screen support cords, various cords in automobiles and aircraft, power transmission cords of electric products and robots, etc. The core-sheath composite fiber of the present invention is homogeneous in all directions of the fiber cross section Since the characteristics can be exhibited, monofilaments used for textiles for industrial materials and the like are particularly effective applications.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited at all by this. The various characteristics of the present invention were evaluated by the following methods.
(1) Tensile strength / elongation, elastic modulus: In accordance with the method described in JIS L1013 (1999), using a Tensilon UCT-100 manufactured by Orientec under the conditions of a sample length of 100 mm and a tensile speed of 50 mm / min, a solid phase The physical properties after polymerization were measured.
(2) Melt viscosity: Measured using a Capillograph type 1B manufactured by Toyo Seiki Co., Ltd.
(3) Melting point: In the differential calorimetry performed by a differential scanning calorimeter (DSC) manufactured by PerkinElmer Co., Ltd., for liquid crystal polyester, an endothermic peak observed when measured at room temperature to 40 ° C./min. After observing the temperature (Tm ₁ ), holding at a temperature of approximately Tm ₁ + 20 ° C. for 5 minutes, cooling to 50 ° C. at a rate of temperature decrease of 20 ° C./min, and measuring again at a temperature increase condition of 20 ° C./min The endothermic peak temperature (Tm ₂ ) observed in FIG. For the flexible polymer, the endothermic peak temperature (Tm ₃ ) observed when measured under the temperature rising condition of 16 ° C./min using the same apparatus was defined as the melting point.
(4) Abrasion resistance: A monofilament was used as an evaluation sample, and the end of the sample was applied to a φ4 mm ceramic rod guide (bar guide manufactured by Yuasa Yarnichi Kogyo Co., Ltd .: material YM-99C, hardness 1800) at a contact angle of 100 °. Gripping the sample at a stroke length of 30 mm and a stroke speed of 100 times / minute while holding a stroke device and applying a tension of 5.0 cN / dtex, stopped every 10 strokes, The presence or absence of fibrils on the surface of the sample was observed, and the number of strokes when any occurrence was confirmed was measured. The measurement was performed 10 times per 1 m per sample.
(5) The thickness of the sheath component, the composite ratio of the liquid crystal polyester, and the component confirmation of the polymer alloy part: determined from the entire cross-sectional image of the single yarn taken with a transmission electron microscope (TEM (H-800 type, manufactured by Hitachi, Ltd.)) . The composite ratio of the liquid crystal polyester in the core component and the sheath component was measured by Mitani Corp. for a photograph of the cross section of the fiber taken at a magnification of 5,000 with a transmission electron microscope (TEM (H-800, manufactured by Hitachi, Ltd.)). Using the image processing software (Winroof) manufactured by the company, the core component and the sheath component are determined by etching the core-sheath component interface, and the composite occupying per unit area of the liquid crystal polyester (component shown in white) in each component Confirmed by determining the percentage.

Reference example 1
As the liquid crystal polyester, a liquid crystal polyester in which 72 mol% of the structural units generated from p-hydroxybenzoic acid account for 28 mol% of the entire structural units generated from 6-hydroxy 2-naphthoic acid was used. The melt viscosity of this liquid crystal polyester was 115 Pa · s at a measurement temperature of 300 ° C. and a shear rate of 100 sec ⁻¹ , and the melting point was 278 ° C. (hereinafter, this polymer is referred to as LCP1).

As the flexible polymer, polyethylene naphthalate obtained by polycondensation of 2,6-naphthalenedicarboxylic acid and ethylene glycol was used. The polyethylene naphthalate had a melt viscosity of 350 Pa · s at a measurement temperature of 300 ° C., a shear rate of 100 sec ⁻¹ , and a melting point of 268 ° C. (hereinafter, this polymer is referred to as PEN1).

The core component was LCP1 and the sheath component was PEN1, and the core component and the sheath component were melted by separate extruders and supplied to a spinning pack, and melt spinning was performed using a core-sheath type composite die as shown in FIG. The core component restricting portion of the base has a cross-sectional area of 0.13 mm ² , the stabilizing flow path has 10 mm, and the terminal end portion of the stabilizing flow path has a core component second constricting section having a cross-sectional area of 0.38 mm ^2. . On the other hand, the sheath component used was a core-sheath type composite die in which three sheath component restricting portions having a cross-sectional area of 0.07 mm ² were arranged at 120 ° intervals concentrically with the flow axis of the core component. The number of discharge holes was 10, and discharge was performed at a spinning temperature of 315 ° C. so that the ratio of the core component to the sheath component was 7: 3, and winding was performed at a spinning speed of 600 m / min to obtain a 100 dtex multifilament. At this time, there was no clogging of discharge holes, discharge bending, etc., and the yarn forming property was good.

  100 g of this spinning raw material is wound on a solid-state polymerization bobbin in which a heat-resistant nonwoven fabric is wound around a metal cylinder that allows gas to pass through, and nitrogen gas is supplied for 5 hours at 200 ° C., 5 hours at 230 ° C., and 20 hours at 260 ° C. Solid state polymerization was conducted while passing through. The obtained solid phase polymerized yarn had a strength of 16.4 cN / dtex, an elongation of 3.2%, and an elastic modulus of 450 cN / dtex, and had the performance described in Table 1.

Example 1
Reference Example 1 except that a polymer alloy chip prepared by mixing LCP1 with PEN1 so that the composite ratio is 20% by weight and melting and kneading with a biaxial extruder (screw diameter φ15 mm) was used as a sheath component. Spinning was carried out in the same manner. This spinning raw yarn was subjected to solid phase polymerization in the same manner as in Reference Example 1 to obtain solid phase polymerization yarns shown in Table 1.

Example 2
PEN1 was mixed with the core component so that the composite ratio of LCP1 was 70% by weight, and the same method as in Example 1 was used, except that a polymer alloy chip prepared by melting and kneading in the same manner as in Example 1 was used. Spinned. At this time, there was no clogging of discharge holes, discharge bending, etc., and the yarn forming property was good.

  This spinning yarn was subjected to solid phase polymerization in the same manner as in Example 1 to obtain solid phase polymerization yarns shown in Table 1.

Example 3
A filament of 50 dtex was obtained by spinning in the same manner as in Example 1 except for winding at a spinning speed of 1200 m / min. This spinning raw yarn was subjected to solid phase polymerization in the same manner as in Reference Example 1 to obtain solid phase polymerization yarns shown in Table 1.

Example 4
A filament of 50 dtex was obtained by spinning in the same manner as in Example 1 except for winding at a spinning speed of 1200 m / min. This spinning raw yarn was subjected to solid phase polymerization in the same manner as in Reference Example 1 to obtain solid phase polymerization yarns shown in Table 1.

Comparative Example 1
Spinning was carried out in the same manner as in Example 2 except that a core-sheath type composite die having no core component restricting portion was used. This spinning yarn was subjected to solid phase polymerization in the same manner as in Example 1 to obtain solid phase polymerization yarns shown in Table 2.

Comparative Example 2
Spinning was performed in the same manner as in Comparative Example 1 except that a core-sheath type composite die having a core component second constriction part having a cross-sectional area of 0.13 mm ² was used at the terminal end of the stabilization flow path. This spinning yarn was subjected to solid phase polymerization in the same manner as in Example 1 to obtain solid phase polymerization yarns shown in Table 2.

Comparative Example 3
Spinning was performed in the same manner as in Example 2 except that the cross-sectional area of the sheath component restricting portion was 0.38 mm ² . This spinning yarn was subjected to solid phase polymerization in the same manner as in Example 1 to obtain solid phase polymerization yarns shown in Table 2.

Comparative Example 4
The same method as in Example 1 except that the sheath component as shown in Patent Documents 1 to 4 does not pass through the narrowed portion having a cross-sectional area of 0.2 mm ² or less and is joined from the entire circumferential direction. Was spun. This spinning yarn was subjected to solid phase polymerization in the same manner as in Example 1 to obtain solid phase polymerization yarns shown in Table 2.

  In each of Comparative Examples 1 to 4, Tmax / Tmin exceeded 2, and the abrasion resistance was inferior to that of the example.

It is the schematic which shows an example of the core sheath composite nozzle | cap | die for obtaining the core sheath type composite fiber of this invention.

Explanation of symbols

1: Core component constriction part 2: Stabilization flow path 3: Core sheath component confluence part 4: Composite flow inflow hole 5: Discharge hole 6: Core component inflow hole 7: Core component second constriction part 8: Sheath component constriction part

Claims (4)

Unrealized 50 wt% or more of the liquid crystal polyester in the core component, and a composite ratio Rs of the liquid crystal polyester in the sheath component is in the range of less than 15 wt% to 50 wt%, including the core together liquid crystal polyester core component and sheath component are A core-sheath characterized in that the relation between the maximum value (Tmax) and the minimum value (Tmin) of the thickness of the sheath component in the fiber cross section satisfies Tmax / Tmin ≦ 2.0. Type composite fiber.   The core-sheath-type composite fiber according to claim 1, wherein the cross section of the fiber is a round cross section and is a concentric circle. The core-sheath type composite fiber according to claim 1 or 2 , wherein the dispersion component in the sheath component is a liquid crystalline polyester. The core-sheath-type conjugate fiber according to any one of claims 1 to 3 , wherein the dispersed component of the core component and the sheath component is a liquid crystal polyester.