JP4706438B2 - High strength composite fiber - Google Patents

Description

  The present invention relates to a composite fiber having high strength and excellent wear resistance, fatigue resistance, and heat resistance, and is used in general industrial materials, particularly ropes, rubber reinforcement, geotextiles, FRC applications, computers. It is widely used for ribbons, printed circuit boards, airbags, bag filters, screen bags, etc.

It is known that the fiber of the melt liquid crystal forming polyester (A) has high strength and high elastic modulus because the molecular chain is highly oriented in the fiber axis direction. However, since only weak intermolecular forces act in the direction perpendicular to the fiber axis, fibrils are easily generated by friction, causing trouble. In addition, kink bands and buckling phenomena are likely to occur, and since they tend to concentrate locally, the fatigue resistance is low. For the purpose of improving these drawbacks, a core-sheath composite fiber in which a bendable thermoplastic resin (B) is combined and a core-sheath composite fiber in which a sheath component and the entire fiber are alloyed has been proposed. (Patent Documents 1 to 4)
However, since the fibers are solid-phase polymerized at a temperature close to the melting point for further strengthening, only the melting point peak is observed in the differential scanning calorimetry (hereinafter referred to as DSC) measurement, and it is known that the fibers are almost crystallized. As described above, since the crystallization of the flexible thermoplastic resin (B) proceeds excessively and becomes brittle, there is a limit to improving the wear resistance of the composite fiber.

In addition, although the yarn before solid-state polymerization retains sufficient strength compared to general polyester, it is low in strength to be called high-strength fiber, and in solid-state applications where high strength is required. Strengthening by polymerization was an essential requirement.
JP-A-4-272226 (Claims) JP-A-8-260249 (Claims) JP-A-14-317334 (Claims) JP 2003-239137 A (Claims)

  The present invention is compounded with a solid-phase-polymerized molten liquid crystal forming polyester (A), which has been difficult with conventional high-strength technology in molten liquid crystal forming polyester (A) fibers with improved wear resistance. It is intended to provide a composite fiber that can greatly improve the wear resistance by further amorphizing the flexible thermoplastic resin, and can further reduce the fineness.

  As a result of investigations to solve the above problems, the present inventors have found that a single molten liquid crystal-forming polyester fiber has a long time for orientation relaxation even when the temperature is raised above the melting point, and has high strength retention, at least It has been found that the wear resistance is improved by heat-treating the melt-formed liquid crystal forming polyester composite fiber having a bendable thermoplastic resin exposed to the fiber surface layer at an appropriate temperature and time. Among them, it was discovered that the wear resistance may be specifically improved depending on the heat treatment conditions. As a result of further investigations, it was found by DSC measurement that the wear resistance is greatly improved when a crystallization peak is observed, and the present invention has been achieved.

That is, this invention is comprised from the following.
(1) Strength 10 cN / dtex or more, molten liquid crystal forming polyester (A) has a core, flexible thermoplastic resin (B) has a sheath-core structure, and melted liquid crystal forming polyester in the sheath component of the core-sheath structure A high-strength composite fiber characterized in that a crystallization temperature peak is observed by differential scanning calorimetry (DSC) measurement in a composite fiber in which (A) is an island and the flexible thermoplastic resin (B) has a sea-island structure .
(2) The high-strength conjugate fiber according to (1), wherein the crystallization heat quantity ΔHc observed by differential scanning calorimetry (DSC) measurement is 3 J / g or more.
(3) The high-strength composite fiber according to (1) or (2), wherein the composite fiber is a monofilament.

  The present invention provides a melt liquid crystal forming polyester (A) fiber with improved abrasion resistance, which has a non-crystalline structure with a solid phase polymerized melt liquid crystal forming polyester (A), which is not present in conventional high strength technology. The thermoplastic thermoplastic resin (B) is a fiber, and the amorphous structure of the flexible thermoplastic resin (B) contributes to a significant improvement in wear resistance. The field of use of the fiber of the present invention is widely used for general industrial materials, especially ropes, rubber reinforcements, geotextiles, FRC applications, computer ribbons, base fabrics for printed boards, air bags, bag filters, screen bags, etc. In particular, it can be suitably used in fields where wear resistance is important.

  Hereinafter, embodiments of the present invention will be described in detail.

  The molten liquid crystal-forming polyester (A) used in the present invention refers to a polyester that exhibits optical anisotropy when heated and melted. This characteristic can be recognized, for example, by placing the sample on a hot stage, heating and heating in a nitrogen atmosphere, and observing the transmitted light of the sample.

  As the molten liquid crystal forming polyester (A) used in the present invention, A.I. A polymer of aromatic oxycarboxylic acid; A polymer of aromatic dicarboxylic acid and aromatic diol, aliphatic diol, C.I. Examples thereof include a copolymer of A and B. Moreover, a conventionally well-known method can be used for the polymerization prescription of molten liquid crystal forming polyester (A).

  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. Aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, diphenyldicarboxylic acid, naphthalene dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylethanedicarboxylic acid, etc., or alkyl, alkoxy, and halogen substituted products of the above aromatic dicarboxylic acids Etc.

  Examples of the aromatic diol include hydroquinone, resorcin, dioxydiphenyl, naphthalenediol, and alkyl, alkoxy, and halogen-substituted products of the above aromatic diol. Aliphatic diols include ethylene glycol, propylene glycol, butanediol, neopentyl glycol, and the like.

  In the present invention, polyesters obtained by polymerizing the above monomers can be widely used. Preferred examples thereof include a copolymer of a p-hydroxybenzoic acid component and an ethylene terephthalate component, a copolymer of a p-hydroxybenzoic acid component, 4,4-dihydroxybiphenyl, terephthalic acid and / or isophthalic acid. P-hydroxybenzoic acid component and 6-hydroxy 2-naphthoic acid component are copolymerized, p-hydroxybenzoic acid component, 6-hydroxy 2-naphthoic acid component, hydroquinone and terephthalic acid are copolymerized Can be used.

  The molten liquid crystal forming polyester (A) used in the present invention preferably has a melting point (hereinafter referred to as Tm) of a resin used for spinning in the range of 260 to 360 ° C, more preferably Tm of 270 to 350 ° C. . Tm was measured by measuring the temperature at which the main endothermic peak observed when the temperature was increased at 16 ° C./min with a differential scanning calorimeter (DSC2920 manufactured by TA instruments).

  Examples of the flexible thermoplastic resin (B) used in the present invention include polyesters, vinyl polymers such as polyolefin and polystyrene, polyarylate, polycarbonate, polyamide, polyimide, polyphenylene sulfide, polyphenylene oxide, polysulfone, aromatic polyketone, Aliphatic polyketones, semi-aromatic polyester amides, polyester ether ketones, fluororesins and the like can be mentioned.

  Among these flexible thermoplastic resins (B), polyphenylene sulfide is preferred from the viewpoint of high heat resistance and solvent resistance.

  From the viewpoint of adhesiveness, polyamides represented by nylon 6, nylon 66, nylon 46, nylon 6T, nylon 9T and the like are preferable.

  Furthermore, from the point of abrasion resistance, preferably polyesters represented by polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycyclohexanedimethanol terephthalate, etc., among these, high heat resistance, thermal decomposition characteristics From the above, polyethylene naphthalate is particularly preferable.

  In the present invention, the flexible thermoplastic resin (B) may contain other copolymer components in a proportion of 20 mol%, more preferably 10 mol% or less. For example, the compound copolymerizable with polyamide includes polyacrylic acid soda, poly N vinylpyrrolidone, polyacrylic acid and its copolymer, polymethacrylic acid and its copolymer, polyvinyl alcohol and its copolymer, cross-linking Examples thereof include, but are not limited to, polyethylene oxide resins. The compounds copolymerizable with polyester include dicarboxylic acids such as terephthalic acid, isophthalic acid, succinic acid, cyclohexanedicarboxylic acid, adipic acid, dimer acid, and sebacic acid as acidic components, and ethylene glycol, diethylene glycol, and butane as glycol components. Examples thereof include, but are not limited to, diol, neopentyl glycol, cyclohexane dimethanol, polyethylene glycol, and polypropylene glycol.

  The molten liquid crystal-forming polyester (A) and the flexible thermoplastic resin (B) used in the present invention are inorganic materials such as various metal oxides, kaolin, silica and the like within a range not impairing the effects of the present invention. A small amount of additives such as additives, matting agents, flame retardants, antioxidants, ultraviolet absorbers, infrared absorbers, crystal nucleating agents, fluorescent brighteners, and end group blocking agents may be contained.

  The composite fiber of the molten liquid crystal forming polyester (A) and the flexible thermoplastic resin (B) of the present invention requires a strength of 10 cN / dtex or more, and is made of general nylon by setting the strength to 10 cN / dtex or more. Differentiating from high-strength fibers of polyester, it can be suitably used in fields where higher strength is required. A preferable strength range is 10 cN / dtex or more and 40 cN / dtex or less.

  In addition, it is important that the crystallization temperature peak of the conjugate fiber of the present invention is observed by differential scanning calorimetry (DSC) measurement. The observation of the crystallization temperature peak means that the composite fiber has an amorphous part, and the presence of this amorphous part can improve the wear resistance. When this crystallization temperature peak is not observed by DSC measurement, it means that it is almost crystallized, and the flexible thermoplastic resin (B) is also improved in strength but becomes brittle and has a large wear resistance. I cannot expect improvement.

  The high-strength conjugate fiber of the present invention preferably has a crystallization heat amount ΔHc of 3 J / g or more observed by differential scanning calorimetry (DSC) measurement. By setting the crystallization heat amount ΔHc to 3 J / g or more, the amorphous portion can have an amorphous amount sufficient to express an improvement in wear resistance. More preferably, it is 4 J / g or more.

  For the composite fiber of the present invention, a known composite method such as sea-island composite, blend, alloy, core-sheath composite can be used.

It is preferable that at least the flexible thermoplastic resin (B) is exposed on the fiber surface layer of the composite fiber composed of the molten liquid crystal-forming polyester (A) and the flexible thermoplastic resin (B) used in the present invention. This is because the effect of suppressing the fibrillation of the molten liquid crystal forming polyester (A) is exhibited by the flexible thermoplastic resin (B) coming out on the surface layer, thereby improving the wear resistance. Figured. At this time, the ratio of the flexible thermoplastic resin (B) exposed to the fiber surface layer is preferably 50% or more, and more preferably 70% or more. By making the ratio of the flexible thermoplastic resin (B) exposed to the fiber surface layer 50% or more, the effect of improving the wear resistance is further increased. Here, the ratio of the flexible thermoplastic resin (B) exposed to the fiber surface layer can be measured by performing cross-sectional observation with a transmission microscope (TEM).
The composite fiber used in the production method of the present invention preferably has a sea-island structure in which the molten liquid crystal-forming polyester (A) is an island and the flexible thermoplastic resin (B) is a sea. By forming a sea-island structure using the flexible thermoplastic resin (B) as a sea component, more flexible thermoplastic resin (B) can be exposed on the surface layer, and the amorphous thermoplastic resin ( B) can improve the wear resistance. Here, the sea-island structure can be observed by observing a cross section with a transmission microscope (TEM).

  As a production method of the sea-island structure composite fiber, a method using a base for sea-island composite or a general method of kneading a molten liquid crystal forming polyester (A) and a flexible thermoplastic resin (B) with a uniaxial kneader or a biaxial kneader. Known methods, such as simple blends, alloy fiber manufacturing methods, and manufacturing methods for producing phase-reversed alloy fibers by using a flexible thermoplastic resin (B) that has a viscosity ratio significantly different from that of the melt-forming liquid crystal forming polyester (A). Can be used.

  The number of island components in the fiber cross section of the sea-island structure is not particularly limited, but is preferably about 10 to 100,000. In the case of a sea-island composite base, an island component having a uniform diameter is formed by changing the number of islands in the composite part. In the blend and alloy production methods, the number of islands and the distribution of island diameters can be adjusted by changing the mixing ratio, melt viscosity, and the like. From the viewpoint of fiber strength and fibril resistance, the island component is preferably fine. For example, the diameter of the island component is preferably about 0.1 to 0.5 μm.

  The ratio of molten liquid crystal forming polyester (A) and flexible thermoplastic resin (B) having a sea-island structure is not particularly limited and can be used in a general sea-island composite ratio. In view of the properties, it is preferable that the molten liquid crystal forming polyester (A) is 50% or more and 80% or less.

The composite fiber used in the present invention is preferably a core-sheath structure in which the molten liquid crystal-forming polyester (A) is a core component and the flexible thermoplastic resin (B) is a sheath component. By having a core-sheath structure, the flexible thermoplastic resin (B) is substantially disposed on the fiber surface layer, so that the effect of heat treatment is sufficiently exhibited. At this time, by making the sheath component into a sea-island structure of a flexible thermoplastic resin (B) and a molten liquid crystal forming polyester (A), the interface adhesion between the sheath component and the core component can be made stronger and peeling can be prevented. Therefore, it is preferable. As a method for producing the core-sheath structure fiber, a method of coating the yarn once spun can be used in addition to a method of using a core-sheath die.
The core-sheath ratio in the core-sheath structure can be used as long as it is a general core-sheath ratio, but considering the high strength and wear resistance, the ratio of the core component is preferably 50% or more and 85% or less. Furthermore, in order to suppress core-sheath interface peeling, it is also possible to blend a polymer having high compatibility with the flexible thermoplastic resin (B) of the sheath component into the molten liquid crystal forming polyester (A) of the core component.

  When the sheath component is a sea-island structure of molten liquid crystal forming polyester (A) and flexible thermoplastic resin (B), the molten liquid crystal forming polyester (A) component is 50% or less and the thermoplastic fiber is flexible on the fiber surface layer. It is preferable to increase the exposure of the resin (B) and improve the wear resistance.

  The composite fiber of the present invention can be used in the form of a multifilament, a monofilament or the like.

  When used for industrial use, the multifilament preferably has a total fineness of 10 dtex or more and 3000 dtex or less.

  The fiber diameter of the monofilament is preferably 10 μm to 2000 μm, and in order to further exert the effect of the present invention, a fine filament monofilament of 10 μm to 100 μm is preferable.

  The cross-sectional shape of the conjugate fiber of the present invention is not particularly limited, and is not limited to a normal circular cross section, but also a Δ cross section, a Y-shaped cross section, a □ cross section, a cross section, a hollow cross section, a C-shaped cross section, a rice field cross section, and the like. Any irregular cross section can be adopted. Among these, in the case of using for screens, the cross-sectional shape is preferably circular in order to obtain a uniform opening.

  A typical method for producing the conjugate fiber of the present invention is shown below.

  The conjugate fiber of the present invention is prepared by mixing a melted liquid crystal forming polyester (A) and a flexible thermoplastic resin (B), for example, in a pellet state, and melting and kneading with a biaxial extruder. Discharge more, take up while cooling, melt liquid crystal-forming polyester (A) and flexible thermoplastic resin (B) with separate extruders, and use a composite base such as a core sheath base or a sea island base Thus, a composite yarn can be obtained by discharging while performing core-sheath and sea-island composite and winding it while cooling. This composite yarn is preferably solid-phase polymerized in an inert gas atmosphere at a melting point of the molten liquid crystal forming polyester (A) of about -10 ° C. for several minutes to several tens of hours. It can manufacture by heat-processing at the temperature more than melting | fusing point of a thermoplastic resin (B).

  Since the flexible thermoplastic resin (B) crystallized by solid phase polymerization is returned to the amorphous state by this heat treatment, the effect of the present invention is exhibited. At this time, the heat treatment may be performed continuously after the solid-phase polymerization or may be performed after winding. However, in order to heat the resin to a temperature higher than the melting point of the flexible thermoplastic resin (B), it is wound around a metal bobbin and solidified. In the case of a batch type solid phase polymerization method in which phase polymerization is performed, heat treatment is preferably performed at the time of rewinding or after rewinding in order to prevent fusion between fibers.

  The reason why the abrasion resistance is improved by the heat treatment is that the single molten liquid crystal-forming polyester (A) fiber has a long time for orientation relaxation even when the temperature is raised to the melting point or higher, and has high strength retention. Heat treatment is performed at an appropriate temperature and time at which the relaxation of the orientation of the flexible thermoplastic resin (B) in the solid-phase polymerized composite fiber in which the resin (B) is exposed on the fiber surface layer and further the amorphous state proceeds. Thus, while maintaining the strength of the molten liquid crystal-forming polyester (A), the improvement in wear resistance due to the structural change of the flexible thermoplastic resin (B) directly leads to the improvement in wear resistance of the composite fiber. The presence of the melt-forming liquid-crystalline polyester (A) does not cause problems such as yarn breakage or reduced strength even when the structure of the flexible thermoplastic resin (B) is changed to an amorphous state. Theft is born.

  The heat treatment for producing the conjugate fiber of the present invention is carried out in an atmosphere at a melting point of the flexible thermoplastic resin (B) of the solid phase polymerized conjugate fiber (B) + 20 ° C. or more and below the temperature at which the conjugate fiber is melt-cut. It is preferable to perform a high-temperature short-time heat treatment in a time period of 0.001 seconds to 5 seconds. The heat treatment can be efficiently performed such that the effect of the heat treatment is easily generated in a short time by setting the melting point of the flexible thermoplastic resin (B) to 20 ° C. or more, and the influence on the strength of the melted liquid crystal forming polyester (A) can be reduced. Can be done. The heat treatment temperature may be within a general heater temperature control range, and is preferably melting point + 20 ° C. or higher, melting point + 500 ° C. or lower, more preferably melting point + 30 ° C. or higher and melting point + 300 ° C. or lower.

  The heat treatment time is preferably 0.001 second or more and 5 seconds or less. The fiber can be prevented from fusing while maintaining an efficient heat treatment within this time range. The heat treatment time is preferably 0.005 seconds to 2 seconds, more preferably 0.01 seconds to 1 second.

  The heat treatment for producing the conjugate fiber of the present invention is preferably a non-contact heat treatment in order to suppress fluff generation in the process and to perform a uniform heat treatment. As a preferable heat source, a slit heater using a general plate heater, laser heating, or the like can be used.

  The field of application of the composite fiber of the present invention is widely used for general industrial materials, especially ropes, rubber reinforcements, geotextiles, FRC applications, computer ribbons, printed circuit boards, airbags, bag filters, screen bags, etc. In particular, it can be suitably used in a field where wear resistance is important.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto.
[Differential scanning calorimetry (DSC) measurement]
Measurement was performed from room temperature to 320 ° C. with a temperature rising time of 16 ° C./min for 1st RUN using DSC2920 manufactured by TA instruments.
[Strong elongation, elastic modulus]
Measurement was performed using Tensilon UCT-100 manufactured by Orientec Co., Ltd. according to JIS L1073 (1965).
[Melt viscosity]
It measured using the Toyo Seiki Capillograph 1B.
[Abrasion resistance]
For evaluation of abrasion, thread (heat-treated yarn) was applied to a 3 mm satin metal rod with a contact angle of 35 °, a load of 3 cN / dtex was hung, a reciprocating motion was applied at a stroke length of 30 mm, and a speed of 100 times / min. The number of reciprocations at the time when fluff accompanied by fibrillation occurred was measured.

Reference Examples 1 and 2 and Comparative Examples 1 to 3
The molten liquid crystal forming polyester (A) is composed of a structural unit (1) formed from p-hydroxybenzoic acid and a structural unit (2) generated from 6-hydroxy-2-naphthoic acid. The molten liquid crystal forming polyester (A) in which 72 mol% of the structural unit (2) accounts for 28 mol% was used. The melting point of this molten liquid crystal forming polyester (A) was 278 ° C., and the melt viscosity at a measurement temperature of 300 ° C. and a shear rate of 100 sec ⁻¹ was 110 Pa · s.

Polyethylene naphthalate was used as the flexible thermoplastic resin (B). This polyethylene naphthalate had a melting point of 266 ° C., a measurement temperature of 300 ° C., and a melt viscosity at a shear rate of 100 sec ⁻¹ was 250 Pa · s.

In a pellet state, melted liquid crystal forming polyester (A) and polyethylene naphthalate are mixed at a composite weight ratio of 60/40, and melted and kneaded at a screw rotation speed of 200 rpm by a biaxial extruder (screw diameter φ15 mm). A nozzle having a nozzle diameter of 0.13 mm, a nozzle length of 0.26 mm, and a 48-hole die was discharged at a spinning temperature of 310 ° C. and wound at a spinning speed of 600 m / min to obtain a 265 dtex filament. At this time, there was no discharge hole clogging, no discharge bending, etc., and the spinning property was good. Regarding the resin composition of the sea-island component, the island component was composed of molten liquid crystal-forming polyester (A) and the sea component was composed of polyethylene naphthalate. This raw yarn was set as Comparative Example 1 and had the following performance.
Strength 5.6 cN / dtex
Elongation 2.0%
Elastic modulus 252cN / dtex
Abrasion resistance 190 times This spinning yarn was heat-treated in a nitrogen gas atmosphere at 250 ° C. for 6 hours and 260 ° C. for 12 hours. The obtained heat-treated yarn had almost no interfiber sticking and had good unwinding properties. This solid state polymerized yarn was used as Comparative Example 2 and had the following performance.
Strength 12.5 cN / dtex
Elongation 3.2%
Elastic modulus 352cN / dtex
The evaluation result of the wear resistance was 210 times. When the yarn surface after the wear resistance evaluation was observed, the island component of the surface layer in the fiber cross section was peeled off.
This yarn was heat-treated in a heat treatment apparatus having an apparatus width of 40 mm, a slit width of 4 mm, and a heat treatment length of 15 mm by changing the temperature and the treatment speed. The physical properties are shown in Table 1.

Here, DSC charts of Comparative Example 1 of the spinning yarn, Comparative Example 2 of the solid phase polymerized yarn, and Reference Example 1 are shown in FIGS. In FIG. 1, the spinning yarn, polyethylene naphthalate compounded with molten liquid crystal forming polyester has a glass transition point (Tg) of 120 ° C., a crystallization peak (Tc) of 166 ° C., and a melting point (Tm). Observed at 266 ° C., the melting point of the melt-forming liquid crystal forming polyester is 278 ° C. and is buried in the melting point peak of polyethylene naphthalate. The solid yarn polymerized from the original yarn of FIG. 1 is shown in FIG. 2, and the glass transition point (Tg) and crystallization peak disappeared by subjecting the composite fiber to a solid phase polymerization treatment at a temperature of 260 ° C. The melting point (Tm) has risen to 273 ° C. due to the progress of solid-state polymerization and crystallization of phthalate. In FIG. 2, the liquid crystal forming polyester is also solid phase weighted.

The solid phase polymerization yarn is the chart of Example 1 which is heat-treated briefly hot reference to Figure 3, one melting point of the molten liquid forming polyesters are observed in 304 ° C. in the same position before the heat treatment, polyethylene naphthalate The glass transition point (Tg) is 121 ° C. and the crystallization temperature (Tc) is 167 ° C., which is observed at almost the same position as in FIG. 1 of the spinning yarn, and the melting point of polyethylene naphthalate is 258 ° C. Was observed at a lower temperature. From these observation results, it is presumed that polyethylene naphthalate is being relaxed in orientation and amorphous without damaging the physical properties of the melt-forming liquid-crystalline polyester by high-temperature and short-time heat treatment. Is considered to be a reason for the significant improvement.

Reference Examples 3 and 4, Comparative Examples 4 to 6
Using the same melt liquid crystal forming polyester (A) and polyethylene naphthalate as in Reference Example 1, using a composite spinning device, using a core sheath cap, the core component is melt liquid crystal forming polyester (A), and the sheath component is polyethylene. The core-sheath composite ratio is 70/30 so that it becomes naphthalate, and the nozzle diameter is 0.13 mm, the nozzle length is 0.26 mm, and discharged from a 24-hole die at a spinning temperature of 310 ° C., and a spinning speed of 600 m / min. And a filament of 130 dtex was obtained. At this time, there was no clogging of discharge holes, discharge bending, etc., and the yarn forming property was good. This spinning yarn was heat-treated in a nitrogen gas atmosphere at 250 ° C. for 6 hours and at 255 ° C. for 12 hours. The obtained heat-treated yarn had almost no interfiber sticking, good unwinding property, and had the following performance.
Strength 14.3 cN / dtex
Elongation 4.3%
Elastic modulus 299cN / dtex
Moreover, the evaluation result of the wear resistance was 180 times, and when the yarn surface after the wear resistance evaluation was observed, the sheath component was scraped and the core-sheath interface peeling occurred.

  The yarn was heat-treated in a heat treatment apparatus having an apparatus width of 40 mm, a slit width of 4 mm, and a heat treatment length of 40 mm by changing the temperature and the treatment speed. Table 2 shows the physical properties of the spinning yarn as Comparative Example 4 and the solid-phase polymerization yarn as Comparative Example 5.

Examples 5 and 6 and Comparative Examples 7 to 9
A nozzle diameter of 0.13 mm and a nozzle length were the same as in Example 3 except that a resin in which the sheath component was kneaded so that the weight ratio of melted liquid crystal forming polyester (A) / polyethylene naphthalate = 10/90 was used. A multi-filament of 384 dtex was obtained by discharging from a 0.26 mm, 96-hole die at a spinning temperature of 310 ° C. and winding at a spinning speed of 600 m / min. At this time, there was no clogging of discharge holes, discharge bending, etc., and the yarn forming property was good. The spinning yarn was heat-treated in a nitrogen gas atmosphere at 250 ° C. for 6 hours and 260 ° C. for 12 hours. The obtained heat-treated yarn had almost no interfiber sticking, good unwinding property, and had the following performance.
Strength 14.5 cN / dtex
Elongation 3.9%
Elastic modulus 335cN / dtex
Further, the evaluation result of the abrasion resistance was 250 times, and when the yarn surface after the abrasion resistance evaluation was observed, the sheath component was scraped.

  This yarn was heat-treated using a heat treatment apparatus having an apparatus width of 40 mm, a slit width of 4 mm, and a heat treatment length of 15 mm, changing the temperature and the treatment speed. Table 3 shows the physical properties of the spinning yarn as Comparative Example 7 and the solid-phase polymerization yarn as Comparative Example 8.

Reference Examples 7 and 8, Comparative Examples 10 to 12
The same apparatus as in Example 5 was used except that the sheath component was a resin obtained by kneading molten liquid crystal-forming polyester (A) and polyethylene naphthalate at a weight ratio of 90/10, using a nozzle diameter of 0.13 mm, a nozzle length of 0.1 mm. A monofilament of 10 dtex was obtained by discharging from a die of 26 mm and 10 holes at a spinning temperature of 310 ° C. and winding each monofilament at a spinning speed of 600 m / min. At this time, there was no clogging of discharge holes, discharge bending, etc., and the yarn forming property was good. The spinning yarn was heat-treated in a nitrogen gas atmosphere at 250 ° C. for 6 hours and 260 ° C. for 14 hours. The obtained heat-treated yarn had almost no interfiber sticking, good unwinding property, and had the following performance.
Strength 14.5 cN / dtex
Elongation 3.5%
Elastic modulus 373cN / dtex
Further, the evaluation result of the abrasion resistance was 270 times, and when the yarn surface after the abrasion resistance evaluation was observed, the sheath component was scraped.

  The yarn was heat-treated using a heat treatment device having an apparatus width of 40 mm, a slit width of 4 mm, and a heat treatment length of 40 mm, changing the temperature and the treatment speed. Table 4 shows the physical properties of the spinning yarn as Comparative Example 10 and the solid phase polymerized yarn as Comparative Example 11.

DSC chart immediately after spinning DSC chart after solid state polymerization DSC chart of high strength composite fiber

Claims (3)

The strength is 10 cN / dtex or more, the melt liquid crystal forming polyester (A) is a core, the flexible thermoplastic resin (B) is a sheath, and the sheath component of the core sheath structure is the melt liquid crystal forming polyester (A). A high-strength composite fiber characterized in that a crystallization temperature peak is observed by differential scanning calorimetry (DSC) measurement in a composite fiber in which the flexible thermoplastic resin (B) has a sea-island structure . The high-strength conjugate fiber according to claim 1, wherein the crystallization heat amount ΔHc observed by differential scanning calorimetry (DSC) measurement is 3 J / g or more. The high-strength conjugate fiber according to claim 1 or 2, wherein the conjugate fiber is a monofilament.

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