Liquid crystal polyester fiber and method for manufacturing the same

Abstract

The present invention provides liquid crystal polyester fibers which are capable of achieving improved weather resistance without having an ultraviolet absorbent kneaded in the fibers or having an ultraviolet absorbent that has weather resistance adhere to the fibers after spinning.　The present invention provides liquid crystal polyester fibers which are formed substantially only of a liquid crystal polyester and use 5% by mass or less of an ultraviolet absorbent, while having a strength retention ratio of 60% or more in a weather fastness test with respect to light of a xenon arc lamp in accordance with JIS L0843.

Description

[Technical Field]

[0001] This invention relates to liquid crystal polyester fibers and a method for producing the same. [Background technology]

[0002] As high-strength polyester fibers, liquid crystal polyester fibers consisting of aromatic dicarboxylic acids, aromatic diols and / or aromatic hydroxycarboxylic acids and their derivatives are used. For example, liquid crystal polyester fibers can be obtained by melt-spinning a liquid crystal polyester polymer containing p-hydroxybenzoic acid or 6-hydroxy-2-naphthalenecarboxylic acid, forming fibers, and then heat-treating them to promote solid-phase polymerization.

[0003] These liquid crystal polyester fibers are known to have poorer weather resistance compared to ordinary polyester fibers and are not suitable for use in environments exposed to light, such as outdoors. Therefore, when used outdoors, measures are taken to prevent exposure to ultraviolet rays, such as covering the fibers with highly weather-resistant materials or covering the outside of the fibers with a weather-resistant agent.

[0004] For example, Patent Document 1 discloses a method in which a resin composition liquid containing carbon black and an ultraviolet absorber is applied to molten anisotropic polyester fibers using a dip-nip method, and then coated with a resin that is substantially free of additives. Patent Document 2 proposes a melt-isotropic aromatic polyester fiber containing 0.5 to 10 wt% of an ultraviolet absorber in the fiber. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 5-287680 [Patent Document 2] Japanese Patent Publication No. 2015-175075 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, while weather resistance is improved in Patent Document 1, there is a problem in that, because an ultraviolet absorber is applied in a later process, the agent tends to fall off with repeated use, and durability cannot be expected. Patent Document 2 describes a method in which an ultraviolet absorber is kneaded into the fiber, which has the problem of reducing the strength of the fiber.

[0007] Therefore, the present invention aims to solve the above-mentioned problems and to obtain liquid crystal polyester fibers that can improve weather resistance without kneading a large amount of ultraviolet absorber into the fibers or attaching a weather-resistant ultraviolet absorber after spinning the fibers. [Means for solving the problem]

[0008] To achieve the above objective, the inventors arrived at the present invention by conducting studies on resin composition and fiber manufacturing methods. The present invention relates to a fiber made of liquid crystal polyester, The amount of UV absorber used is 5% by mass or less. This is a liquid crystal polyester fiber that has a strength retention rate of 60% or more in the weathering fastness test against xenon arc light according to JIS L0891.

[0009] The above-mentioned liquid crystal polyester fibers preferably have an inter-fiber entanglement degree of 10 or less. The above-mentioned liquid crystal polyester fiber preferably has a total fineness of 600 dtex or less. The above-mentioned liquid crystal polyester fiber preferably has a single-fiber fineness of 25 dtex or less. The above-mentioned liquid crystal polyester fiber is preferably obtained by solid-phase polymerization of liquid crystal polyester fiber whose surface does not melt after 1 hour at 250°C.

[0010] The above liquid crystal polyester is preferably a copolyester composed of 6-hydroxy-2-naphthoic acid, terephthalic acid, hydroquinone, and 2,6-naphthalenedicarboxylic acid.

[0011] The present invention relates to a process for melt-spinning a liquid crystal polyester resin at a shear rate of 1×10 , , , ,

[0014] ,

[0015] ~1×10 6 sec -1 , and a spinning draft of 5 to 50 (step 1), and subjecting the fibers obtained in step (1) to heat treatment at a temperature of the melting point of the liquid crystal polyester resin - 60°C to the melting point of the liquid crystal polyester resin - 10°C for solid-phase polymerization (step 2). The method for producing a liquid crystal polyester fiber according to any one of the above is also characterized by having the above steps.

[0012] In the above step (1), it is preferable that the spun fibers obtained by spinning are wound around a first bobbin, and the wound spun fibers are wound around a second bobbin and then subjected to step (2).

Effects of the Invention

[0013] [[ID=​​​​​​​​​​​​ In order to achieve such an object, the above object is achieved by appropriately adjusting the selection of the liquid crystal polyester resin to be used, the manufacturing conditions of the fiber, and the like.

[0016] <Liquid crystal polyester resin> The liquid crystal polyester fiber of the present invention is These consist of aromatic dicarboxylic acids, aromatic diols and / or aromatic hydroxycarboxylic acids and their derivatives, and optionally include copolymers of these with alicyclic dicarboxylic acids, alicyclic diols, aliphatic diols and their derivatives. Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, 4,4'-dicarboxybiphenyl, 2,6-naphthalenedicarboxylic acid, 1,2-bis(4-carboxyphenoxy)ethane, and those in which the hydrogen atoms of the aromatic rings are substituted with alkyl, aryl, alkoxy, or halogen groups. Examples of aromatic diols include hydroquinone, resorcinol, 4,4'-dihydroxybiphenyl, 4,4'-dihydroxybenzophenone, 4,4'-dihydroxydiphenylmethane, 4,4'-dihydroxydiphenylethane, 2,2-bis(4-hydroxyphenyl)propane, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfide, 2,6-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, and others, as well as those in which the hydrogen atoms of the aromatic rings are substituted with alkyl, aryl, alkoxy, or halogen groups. Examples of aromatic hydroxycarboxylic acids include p-hydroxybenzoic acid, m-hydroxybenzoic acid, 6-hydroxy-2-naphthalenecarboxylic acid, 1-hydroxynaphthalene-5-carboxylic acid, and others, as well as those in which the hydrogen atoms of the aromatic rings are substituted with alkyl, aryl, alkoxy, or halogen groups. Examples of alicyclic dicarboxylic acids include trans-1,4-dicarboxycyclohexane, cis-1,4-dicarboxycyclohexane, and those in which the hydrogen atoms of the aromatic rings are substituted with alkyl, aryl, alkoxy, or halogen groups. Examples of alicyclic and aliphatic diols include trans-1,4-dihydroxycyclohexane, cis-1,4-dihydroxycyclohexane, ethylene glycol, 1,4-butanediol, and xylylenediol.

[0017] Among these combinations, preferred aromatic polyesters in the present invention include, for example, copolyesters composed of 6-hydroxy-2-naphthalenecarboxylic acid, terephthalic acid, hydroquinone, and 2,6-naphthalenedicarboxylic acid. In particular, a copolyester comprising 50-70 mol% of 6-hydroxy-2-naphthalenecarboxylic acid, 5-7 mol% of terephthalic acid, 10-30 mol% of hydroquinone, and 15-25 mol% of 2,6-naphthalenedicarboxylic acid is preferred.

[0018] The liquid crystal polyester fiber of the present invention uses an amount of ultraviolet absorber of 5% by mass or less relative to the fiber mass. That is, even with a small amount of ultraviolet absorber used, it has sufficient weather resistance. Therefore, it is acceptable for the amount of ultraviolet absorber used to be 0% by mass. The amount of ultraviolet absorber used is more preferably 3% by mass or less, and even more preferably 2% by mass or less.

[0019] The above-mentioned UV absorbers refer to those commonly used in the textile industry, and include benzophenone-based and benzotriazole-based compounds, as well as titanium dioxide and cerium oxide-based UV absorbers.

[0020] The amount of the above-mentioned UV absorber can be determined by known measurement methods, depending on the type of UV absorber included. For example, in the case of inorganic UV absorbers such as titanium dioxide and cerium oxide, it can be measured by ICP.

[0021] If the liquid crystal polyester fiber of the present invention contains an ultraviolet absorber, the ultraviolet absorber may be kneaded into the fiber or attached to the surface.

[0022] The liquid crystal polyester fiber of the present invention preferably consists substantially of the above-mentioned liquid crystal polyester resin. Specifically, "consisting substantially of liquid crystal polyester resin" means that the liquid crystal polyester resin content is 95% by mass or more of the total fiber, and that no other resins or additives are actively added. Note that oils and other substances used in the manufacturing process of the fiber are not actively added, so fibers to which these substances adhere are included in "consisting substantially of liquid crystal polyester resin".

[0023] The liquid crystal polyester fiber of the present invention is a liquid crystal polyester fiber having a strength retention rate of 60% or more in the weathering fastness test against xenon arc light according to JIS L0891. In the tests described herein, the weathering fastness test according to JIS L0891 is the value measured under the conditions described in the examples. In other words, because it is a fiber that has weather resistance meeting the above standards, it is a fiber that can be suitably used in applications such as heater wire tension members, ropes, and fishing lines, where durability in particularly harsh operating environments is required.

[0024] The liquid crystal polyester fiber of the present invention more preferably has a strength retention rate of 70% or more.

[0025] The liquid crystal polyester fibers of the present invention preferably have an inter-fiber entanglement degree of 10 or less. The above method for measuring the degree of entanglement between single fibers follows the JIS L 1013 method for measuring entanglement: a 100g load is suspended below the fiber, and the thread is allowed to hang vertically. A hook with a 10g load is inserted into the top of the thread, and the degree of entanglement between single fibers is calculated from the descent distance (mm) until the hook stops due to entanglement of the thread, using the following formula. 50 measurements are taken, and the average value is taken as the degree of entanglement between single fibers. Inter-fiber entanglement degree = 1000 / hook drop distance (mm)

[0026] Entanglement between individual fibers occurs when the heat generated during solid-phase polymerization softens the fiber surface, causing the fibers to fuse together. Yarns with fused fibers have low flexibility and are prone to reduced physical properties such as knot strength. Furthermore, when the yarn is rewinded onto another bobbin after solid-phase polymerization in a bobbin package, the fusion acts as a starting point for fibrillation, leading to a decrease in quality. For this reason, it is preferable to have a low level of entanglement between individual fibers, as described above.

[0027] The liquid crystal polyester fiber of the present invention preferably has a strength of 20 cN / dtex or more, as measured under constant-speed elongation conditions as shown in the JIS L 1013 (2010) 8.5.1 standard time test. More preferably, it is 24 cN / dtex or more, and most preferably 28 cN / dtex or more. As mentioned above, liquid crystal polyester fibers containing ultraviolet absorbers may experience a decrease in fiber strength. However, since excellent strength is an important characteristic of liquid crystal polyester fibers, it is preferable that the strength does not decrease. The liquid crystal polyester fiber of the present invention preferably does not use ultraviolet absorbers, or if used, the amount is such that it satisfies the above-mentioned strength range.

[0028] Since liquid crystal polyester fibers are generally used in applications requiring high strength, it is desirable that they possess the aforementioned strength. Furthermore, the liquid crystal polyester fibers of the present invention have excellent effects in that they achieve both weather resistance and low inter-fiber fusion and strength.

[0029] The liquid crystal polyester fiber of the present invention preferably has an elongation of 2 to 5% when measured under the constant-speed elongation conditions specified in JIS L 1013 (2010) 8.5.1 standard time test.

[0030] The liquid crystal polyester fiber of the present invention may be monofilament or multifilament, but multifilament is more preferable. The fiber composition is not particularly limited, but the total fineness is preferably 600 dtex or less. Furthermore, the single filament fineness is preferably 25 tex or less. The above range is preferable because it is suitable for use in a variety of industrial materials.

[0031] The total fineness mentioned above is more preferably 400 dtex or less, and even more preferably 300 dtex or less. The single yarn fineness mentioned above is more preferably 10 dtex or less, and even more preferably 5 dtex or less.

[0032] The lower limit of the total fineness mentioned above is not particularly limited, but it is preferably 4 dtex. More preferably, the lower limit of the total fineness mentioned above is 10 dtex.

[0033] The fineness of the single yarn is more preferably 4 dtex or less, and even more preferably 2 dtex or less.

[0034] The liquid crystal polyester fibers of the present invention are preferable because, having the total fineness and single-fiber fineness described above, they are suitable for use in various industrial materials.

[0035] The weight-average molecular weight (hereinafter referred to as Mw) of the liquid crystal polyester resin used as a raw material in this invention, in terms of polystyrene equivalent, is preferably 30,000 or more, and more preferably 50,000 or more. By setting the Mw to 30,000 or more, an appropriate viscosity is obtained at the spinning temperature, resulting in good spinnability. of The Mw can be increased, and the higher the Mw, the greater the strength, elongation, and modulus of elasticity of the resulting fiber. Furthermore, from the viewpoint of achieving excellent fluidity, an Mw of less than 250,000 is preferable, and less than 150,000 is more preferable. In this invention, Mw refers to the value obtained by the method described in the examples.

[0036] The melting point of the liquid crystal polyester of the present invention is preferably in the range of 200 to 380°C, more preferably 250 to 350°C, and even more preferably 290 to 340°C, from the viewpoint of ease of melt spinning and heat resistance. The melting point was defined as the endothermic peak temperature (Tm2) observed when measuring under heating conditions of 20°C / min from 50°C, holding the material at a temperature of approximately Tm1 + 20°C for 5 minutes, cooling it to 50°C at a rate of 20°C / min, and then measuring it again under heating conditions of 20°C / min.

[0037] The method for producing liquid crystal polyester fibers of the present invention is not particularly limited as long as liquid crystal polyester fibers having the above-described properties can be obtained. By adjusting the composition of the resin used and the manufacturing method, fibers that satisfy the above parameters can be obtained. Specifically, it can be manufactured by, for example, the following manufacturing method. The manufacturing method described in detail below is also part of the present invention.

[0038] The present invention provides a method for producing liquid crystal polyester fibers, Liquid crystal polyester resin with a shear rate of 1 × 10 4 ~1 × 10 6 sec -1 , a process of melt spinning with a spinning draft of 5-50 (1) and, For the fibers obtained by process (1), the melting point of the liquid crystal polyester resin is -6 0 (2) A step in which the liquid crystal polyester resin is heat-treated at the melting point of -10°C to perform solid-phase polymerization. It is characterized by having the following.

[0039] In other words, it is characterized by performing melt spinning with a specific shear rate and spinning draft as described above, and by heating within a specific temperature range during solid-phase polymerization by heat treatment.

[0040] The above step (1) can be carried out according to a general method for manufacturing liquid crystal polyester fibers. An example of a method for manufacturing such liquid crystal polyester fibers will be described in detail below. When extruding the resin, it is preferable to use an extruder-type extruder. The extruded polymer is weighed by a weighing device and, if necessary, after passing through one or two or more foreign matter removal filters, it is led to a die. The foreign matter removal filter is preferably a metal non-woven fabric filter. Also, it is preferable to use a combination of filters with a mesh size of 1 to 100 μm. Further, it is preferable to use a finer filter on the downstream side. The mesh size of the downstream filter is preferably 1 / 2 or less, more preferably 1 / 5 or less, of that of the upstream side.

[0041] At this time, the temperature from the polymer pipe to the die (spinning temperature) is preferably not less than the melting point and not more than the thermal decomposition temperature of the liquid crystal polyester, more preferably not less than the melting point of the liquid crystal polyester + 10°C and not more than 400°C, and even more preferably not less than the melting point of the liquid crystal polyester + 20°C and not more than 370°C. Note that it is also possible to adjust the temperature from the polymer pipe to the die independently. In this case, by making the temperature of the part closer to the die higher than the temperature of its upstream side, the discharge becomes stable.

[0042] In the above step (1), the shear rate is preferably in the range of 1×10 4 ~1×10 6 sec -1 . Being within such a range is preferable in that it is difficult to form orientation spots of molecular chains and the fiber strength is stable. More preferably, it is 5×10 4 ~4×10 5 sec -1 Note that in this specification, the shear rate (sec -1 ) is obtained by the following formula. Shear rate = 4Q / πr 3 (where r is the radius (cm) of the spinning die hole and Q is the polymer discharge amount per hole (cm 3 / sec)) Within the above range, the fiber orientation is sufficient, making it easier to obtain fine-denier fibers and thus easier to achieve the desired physical properties.

[0043] In the above process (1), the spinning draft is between 5 and 50. If the spinning draft is less than 5, fiber diameter unevenness is likely to occur, and if the spinning draft exceeds 50, it will not withstand the draft. re This is desirable because it makes thread breakage more likely. The spinning draft mentioned above is defined as the quotient obtained by dividing the take-up rate by the discharge rate.

[0044] In the present invention, it is preferable that the surface of the liquid crystal polyester fiber before solid-phase polymerization does not melt after 1 hour at 250°C. "The surface does not melt after 1 hour at 250°C" means that when the liquid crystal polyester fiber is treated in a nitrogen atmosphere at 250°C for 1 hour before solid-phase polymerization, and then the fiber bundle is divided into two, fibrillation due to fusion between individual fibers does not occur. This results in extremely low inter-fiber fusion after solid-phase polymerization. La To obtain liquid crystal polyester fibers that fill the meter, it is preferable to gradually apply shear stress during the spinning and melting process until extrusion from the die.

[0045] In step (1) of the method for producing liquid crystal polyester fibers of the present invention, it is preferable to gradually increase the shear rate. In fiber spinning, pressure is applied to a flowing resin, and it is extruded through a spinneret to form a fiber. In this invention, it is preferable to gradually increase the shear rate rather than applying it abruptly. In other words, it is preferable to gradually increase the shear rate rather than rapidly by adjusting the shape and diameter of the equipment's piping, the number of filters, and their mesh size. By doing so, the resin maintains sufficient orientation even in a molten state, and since melt spinning is performed in this state, the resulting fibers have relatively high orientation even before solid-phase polymerization. Furthermore, because of the high orientation, the fiber properties are also good.

[0046] Furthermore, even if the subsequent solid-phase polymerization is carried out at a relatively low temperature (for example, below the melting point of the liquid crystal polyester resin used as a raw material -10°C, more preferably below -15°C, and even more preferably below -20°C), liquid crystal polyester fibers with sufficient strength can be obtained. Liquid crystal polyester fibers obtained by this method have excellent fiber strength and weather resistance, and are less prone to inter-fiber fusion.

[0047] The diameter of the die hole is preferably 0.05 mm or more and 0.2 mm or less. As mentioned above, in order to enable solid-phase polymerization at low temperatures and to gradually increase the shear rate, such a die hole diameter is preferable. The lower limit is more preferably 0.1 mm, and even more preferably 0.07 mm. The upper limit is more preferably 0.15 mm, and even more preferably 0.1 mm.

[0048] Furthermore, in order to improve the productivity of multifilament, the number of holes in a single nozzle is preferably 2 to 1,000, more preferably 5 to 500, and even more preferably 10 to 200.

[0049] The polymer extruded from the die hole passes through a heat retention area and a cooling area to solidify, and is then taken up by a roller (godette roller) rotating at a constant speed. The heat retention area is preferably limited to 400 mm from the die surface, more preferably to 300 mm, and even more preferably to 200 mm, as excessive length would worsen spinning performance. The ambient temperature of the heat retention area can also be increased using a heating means, with a temperature range of 100°C or higher and 500°C or lower, and more preferably 200°C or higher and 400°C or lower. Cooling can be performed using inert gas, air, water vapor, etc., but using a parallel or annular airflow is preferred in terms of reducing environmental impact.

[0050] The draw speed is preferably 50 m / min or more, more preferably 300 m / min or more, and even more preferably 500 m / min or more, in order to improve productivity. The liquid crystal polyester used in this invention has suitable drawability at the spinning temperature, so the draw speed can be increased. There is no particular upper limit, but in the case of the liquid crystal polyester used in this invention, it is about 3,000 m / min from the viewpoint of drawability.

[0051] In this invention, from the viewpoint of improving spinnability and productivity, it is preferable to set the polymer discharge rate to 10 to 2,000 g / min, more preferably to 30 to 1,000 g / min, and even more preferably to 50 to 500 g / min in order to obtain the above-mentioned spinning draft. By setting the rate to 10 to 2,000 g / min, liquid crystal polyester can be obtained with good spinnability.

[0052] The winding can be done using a known winding machine to create packages in the shape of cheese, bread, cone, etc., but it is preferable to use a cheese winding method that allows for a higher winding amount. During winding, there is no problem in using various oils with oiling rollers or oiling nozzles to reduce frictional resistance with the guides and rollers.

[0053] The liquid crystal polyester fibers obtained in this way are preferably subjected to solid-phase polymerization in step (2) in order to further improve their strength and elastic modulus. Solid-phase polymerization can be performed in package form, skein form, tow form (for example, on a metal mesh, etc.), or continuously between rollers to form yarn, but it is preferable to perform it in package form because it simplifies the equipment and improves productivity.

[0054] The present invention more preferably involves winding the spun fibers obtained by spinning in step (1) onto a second bobbin from a first bobbin and then subjecting the second bobbin to step (2). Thus, by rewinding the yarn from the first bobbin to the second bobbin after spinning, the winding density can be reduced, which is advantageous because it facilitates the solid-phase polymerization reaction.

[0055] Solid-phase polymerization can be carried out in an inert gas atmosphere such as nitrogen, an oxygen-containing active gas atmosphere such as air, or under reduced pressure. However, it is preferable to carry it out in a nitrogen atmosphere to simplify the equipment and prevent oxidation of fibers or deposits. In this case, the atmosphere for solid-phase polymerization is preferably a low-humidity atmosphere with a dew point of -40°C or lower.

[0056] The solid-phase polymerization temperature is preferably above the melting point of the liquid crystal polyester resin used as the raw material, which is -60°C. Such a high temperature near the melting point allows solid-phase polymerization to proceed rapidly. The solid-phase polymerization temperature can be increased to approximately -15°C or -10°C, the melting point of the liquid crystal polyester fibers used in solid-phase polymerization. Exceeding this range will cause the individual fibers to fuse together during the heating process, resulting in fiber adhesion. Furthermore, gradually or continuously increasing the solid-phase polymerization temperature over time is preferable as it prevents fusion and improves the time efficiency of solid-phase polymerization. In this case, solid-phase polymerization is carried out for several minutes to several tens of hours depending on the desired performance, but to obtain fibers with excellent strength and elastic modulus, it is preferable to reach the maximum temperature (solid-phase polymerization temperature) for 5 hours or more, and more preferably 10 hours or more. Also, since the solid-phase polymerization reaction saturates over time, about 100 hours is sufficient.

[0057] Although the solid-phase polymerized package can be used as a product as is, it is preferable to rewind the solid-phase polymerized package to increase the winding density in order to improve product transport efficiency. When rewinding after solid-phase polymerization, it is preferable to unwind the yarn in a direction perpendicular to the axis of rotation (fiber circumference direction) while rotating the solid-phase polymerized package, in order to prevent the solid-phase polymerized package from collapsing due to unwinding and to suppress fibrillation when peeling off minor fusion, so-called transverse unwinding, and it is preferable to rotate the solid-phase polymerized package by active drive rather than free rotation.

[0058] Furthermore, the liquid crystal polyester fibers in this invention may be treated with various finishing oils depending on the purpose.

[0059] The liquid crystal polyester multifilament of the present invention can be used as a multifilament, or, for example, separated into monofilaments, and can also be suitably used as staple fibers, cut fibers, etc. Furthermore, it can be used as a fibrous structure such as woven fabrics, knitted fabrics, nonwoven fabrics, and braids.

[0060] The liquid crystal polyester fiber of the present invention, specifically the liquid crystal polyester multifilament of the present invention, is widely used in fields such as general industrial materials, civil engineering and construction materials, sports applications, protective clothing, rubber reinforcement materials, electrical materials (especially as tension members), acoustic materials, and general clothing. Effective applications include screen mesh, filters, ropes, nets, fishing nets, computer ribbons, base fabrics for printed circuit boards, canvases for papermaking, airbags, base fabrics for airships and domes, motorcycle suits, fishing lines, various lines (yachts, paragliders, balloons, kite strings), blind cords, support cords for screen doors, various cords inside automobiles and aircraft, and power transmission cords for electrical products and robots. In particular, it can be suitably used in applications such as heater wire tension members, ropes, and fishing lines. [Examples]

[0061] The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the examples described below. The physical properties and evaluations in the examples were performed as follows.

[0062] 1) Tensile test (strength, elongation, modulus of elasticity) In accordance with JIS L 1013 (2010), a tensile testing machine RTA-100 from Orientec Co., Ltd. was used, and measurements were taken 10 times with a sample length of 200 mm and a tensile speed of 200 mm / min. The average value was then expressed.

[0063] 2) Weather resistance evaluation In accordance with JIS L 0891, the heat-treated yarn was subjected to irradiation at a density of 150 W / m² using a xenon weather meter (model: XEL-1WN) manufactured by Suga Test Instruments Co., Ltd. 2 A lightfastness test was conducted by irradiating the material for 60 hours under the conditions of (300-400nm), black panel temperature of 63°C, and chamber humidity of 50%RH. The strength retention rate was calculated from the strength before and after irradiation. Note that the strength here is the strength measured by the method described in the tensile test above. A strength retention rate of 60% or more was marked with ○, 30% or more and less than 60% with △, and less than 30% with ×. Strength retention rate = (strength after irradiation / strength before irradiation) × 100

[0064] 3) Degree of inter-fiber entanglement In accordance with the JIS L 1013 method for measuring entanglement, a 100g load was suspended below the fiber, and the yarn was allowed to hang vertically. A 10g hook was inserted into the top of the yarn, and the degree of inter-fiber entanglement was calculated from the descent distance (mm) until the hook stopped due to entanglement of the yarn, using the following formula. 50 measurements were taken, and the average value was taken as the degree of entanglement. Inter-fiber entanglement degree = 1000 / Hook drop distance

[0065] [Example 1] As the aromatic polyester, an aromatic polyester polymerized with 55 moles of 6-hydroxy-2-naphthalenecarboxylic acid, 5.5 moles of terephthalic acid, 22.5 moles of hydroquinone, and 17 moles of 2,6-naphthalenedicarboxylic acid was used. The physical properties of this resin showed a melting point of 320°C. The resin was dried in a vacuum dryer at 140°C for 24 hours to a moisture content of 10 ppm. It was then melt-extruded using a 25 mm diameter single-screw extruder, metered with a gear pump, and supplied to a spinning pack. The spinning temperature from the extruder outlet to the spinning pack was 360°C. The spinning pack contained two types of metal nonwoven fabric filters with different pore sizes: the upstream filter had a pore size of 50 μm, and the downstream filter had a pore size of 10 μm. Resin was extruded at a rate of 15 g / min (0.3125 cc / min per pore) from a spinneret with 48 pores, each with a pore diameter of 0.09 mm and a land length of 0.27 mm. The extruded resin was gradually cooled and solidified, then an oil was applied, and all 48 filaments were wound at a rate of 700 m / min. The shear rate at this time was 72,500 sec. -1The spinning draft was set to 17. During the approximately 120 minutes of winding, no yarn breakage occurred, and the spinning performance was good. Next, the yarn was rewound from the spinning bobbin to the heat-treated bobbin at a rate of 300 m / min. During the 100,000 m of rewinding, no single yarn breakage or yarn breakage occurred, and the rewinding was performed well, resulting in good operability. When this fiber was treated in nitrogen at 300°C for 10 hours, fibers with a total fineness of 220.3 dtex, single yarn fineness of 4.6 dtex, strength of 28.5 cN / dtex, elongation of 4.0%, and modulus of elasticity of 550 cN / dtex were obtained.

[0066] [Example 2] The process was carried out in the same manner as in Example 1, except that instead of winding all 48 filaments together, the fibers were divided into eight sections every six filaments before winding. The resulting fibers had a total fineness of 27.8 dtex, a single-filament fineness of 4.6 dtex, a strength of 29.5 cN / dtex, an elongation of 3.8%, and an elastic modulus of 550 cN / dtex.

[0067] [Example 3] Except for winding at a winding speed of 1,400 m / min, the yarn was spun and heat-treated in the same manner as in Example 1 to obtain fibers with a total fineness of 110.3 dtex, a single-filament fineness of 2.3 dtex, a strength of 27.6 cN / dtex, an elongation of 3.8%, and an elastic modulus of 560 cN / dtex.

[0068] [Example 4] The fibers were spun and heat-treated in the same manner as in Example 1, except that a metal nonwoven fabric filter with a pore size of 30 μm on the upstream side and a pore size of 10 μm on the downstream side was used in the spinning pack. The physical properties of the obtained fibers are shown in Table 1.

[0069] [Comparative Example 1] An aromatic polyester polymerized with 73 moles of p-hydroxybenzoic acid and 27 moles of 6-hydroxy-2-naphthalenecarboxylic acid (melting point 290°C) was used as the aromatic polyester, and the heat treatment temperature was 280°C. Except for these differences, the procedure was the same as in Example 1 to obtain a fiber with a total fineness of 220.5 dtex, a single filament fineness of 4.6 dtex, a strength of 23.8 cN / dtex, an elongation of 3.3%, and an elastic modulus of 635 cN / dtex.

[0070] [Comparative Example 2] Except for using an aromatic polyester polymerized with 60 moles of p-hydroxybenzoic acid, 20 moles of biphenol, 5 moles of isophthalic acid, and 15 moles of terephthalic acid (melting point 310°C) as the aromatic polyester, a fiber with a total fineness of 220.8 dtex, a single filament fineness of 4.6 dtex, a strength of 23.7 cN / dtex, an elongation of 2.5%, and an elastic modulus of 1,028 cN / dtex was obtained in the same manner as in Example 1.

[0071] [Comparative Example 3] Fibers were obtained by spinning and heat treatment in the same manner as in Example 1, except that a metal nonwoven fabric filter with a pore size of 10 μm was used in the spinning pack. The physical properties of the obtained fibers are shown in Table 1.

[0072] [Comparative Example 4] Spinning was carried out in the same manner as in Example 1, and the resulting fibers were treated in nitrogen at 320°C for 10 hours to obtain new fibers. The physical properties of the obtained fibers are shown in Table 1.

[0073] [Comparative Example 5] The spinning and heat treatment were carried out in the same manner as in Example 1, except that the filter pore sizes on the upstream and downstream sides of the spinning pack were set to 10 μm, to obtain fibers. The physical properties of the obtained fibers are shown in Table 1. [Comparative Example 6] Fibers were obtained in the same manner as in Comparative Example 1, except that 3% by mass of an ultraviolet absorber was added to the aromatic polyester resin of Comparative Example 1 and spun. The physical properties of the obtained fibers are shown in Table 1. [Example 5] Fibers were obtained in the same manner as in Comparative Example 1, except that 3% by mass of an ultraviolet absorber was added to the aromatic polyester resin of Example 1 and spun. The physical properties of the obtained fibers are shown in Table 1. For "presence or absence of melting after 250°C for 1 hour," "○" indicates that the surface did not melt after 250°C for 1 hour, and "×" indicates otherwise.

[0074] [Comparative Example 7] Spinning was carried out in the same manner as in Comparative Example 3, and the resulting fibers were treated in nitrogen at 320°C for 10 hours to obtain new fibers. The physical properties of the obtained fibers are shown in Table 1.

[0075] [Table 1]

[0076] As is clear from the results in Table 1 above, the fibers of the examples exhibit excellent fiber properties in terms of strength, and high strength retention was also obtained in the weather fastness test using a xenon weatherometer. Furthermore, excellent weather fastness was achieved without the need to knead in large amounts of UV absorbers or to attach weather-resistant UV absorbers after fiber spinning. In addition, the fibers of the examples exhibit excellent fiber properties in terms of the degree of inter-fiber entanglement, and high-quality fibers were obtained in which the individual fibers do not fuse together even after heat treatment by solid-phase polymerization. The fibers of Comparative Examples 1, 3-7 exhibited poor strength retention in weather fastness tests, and the fiber of Comparative Example 2 had remarkably poor weather resistance. Furthermore, the fibers of Comparative Examples 4 and 5 showed a high degree of inter-fiber entanglement, and the fiber of Comparative Example 7 showed fiber adhesion due to fusion between individual fibers. [Industrial applicability]

[0077] The liquid crystal polyester fiber of the present invention can be particularly suitable for use in applications requiring weather resistance, and specifically, for example, it can be particularly suitable for use in applications such as heater wire tension members, ropes, and fishing lines.

Claims

1. A fiber made of liquid crystal polyester, The amount of UV absorber used is 5% by mass or less. The strength retention rate in the weathering fastness test against xenon arc light according to JIS L 0891 is 60% or more. Liquid crystal polyester is a copolyester composed of 6-hydroxy-2-naphthalenecarboxylic acid, terephthalic acid, hydroquinone, and 2,6-naphthalenedicarboxylic acid. Liquid crystal polyester fiber.

2. A liquid crystal polyester fiber according to claim 1, wherein the degree of inter-fiber entanglement is 10 or less.

3. A liquid crystal polyester fiber according to claim 1 or 2, wherein the total fineness is 600 dtex or less.

4. The liquid crystal polyester fiber according to claim 1 or 2, wherein the single filament fineness is 25 dtex or less.

5. The liquid crystal polyester fiber according to claim 1 or 2, which is obtained by solid-phase polymerization of liquid crystal polyester fibers whose surface does not melt after 1 hour at 250°C.

6. Liquid crystal polyester resin with a shear rate of 1 × 10 ４ ~1 x 10 ６ sec －１ , a process of melt spinning in a spinning draft of 5 to 50 (1) and, Step (2) involves heat-treating the fibers obtained in step (1) at a temperature between the melting point of the liquid crystal polyester resin -60°C and the melting point of the liquid crystal polyester resin -10°C to perform solid-phase polymerization. It has, During resin extrusion, an extruder-type extruder is used, and after passing through two or more foreign matter removal filters, the material is guided to the die. The filters used have a mesh size of 1 to 100 μm, with finer filters used downstream. A method for producing liquid crystal polyester fibers according to claim 1 or 2, characterized in that it is the method described in claim 1 or 2.

7. The method for producing liquid crystal polyester fibers according to claim 6, wherein step (1) involves winding the spun fibers obtained by spinning onto a first bobbin, winding the wound spun fibers onto a second bobbin, and then providing them to step (2).

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