Melt-on anisotropic aromatic polyester fiber and method for manufacturing the same

Abstract

The present invention provides a melt-anisotropic aromatic polyester fiber having excellent creep properties. The melt-anisotropic aromatic polyester fiber has a degree of orthorhombicity of 15.0% or more in its crystalline components. For example, the melt-anisotropic aromatic polyester fiber may have a density of 1.4080 g / cm³ or more as determined by a density gradient. Additionally, the melt-anisotropic aromatic polyester fiber may include a melt-anisotropic aromatic polyester having 50 mol% or more of constituent units derived from 4-hydroxybenzoic acid.

Description

Technology Field

[0001] The present application claims priority to Japanese patent application 2022-199790 filed in Japan on December 14, 2022, and incorporates the entirety thereof as part of the present application by reference.

[0002] The present invention relates to a melt-anisotropic aromatic polyester fiber and a method for manufacturing the same. Background Technology

[0003] While general-purpose fibers such as general-purpose polyester fibers are widely used for tension members, super fibers that possess sufficient strength even with a thin wire diameter are attracting attention because the hardening of fine wires in cables and cords is required for the miniaturization of electrical products. In addition, for applications such as optical cables, since communication speed decreases rapidly with slight elongation of the optical fiber, liquid crystal polymer fibers with high dimensional stability (melt-anisotropic aromatic polyester fibers, aramid fibers, etc.) are used. It was known that melt-anisotropic aromatic polyester fibers have excellent dimensional stability because highly oriented spun yarns are obtained in the direction of the fiber axis by spinning, and then the degree of crystallization can be increased by heat-treating the spun yarns to perform solid-state polymerization.

[0004] For example, regarding the crystallinity of molten anisotropic aromatic polyester fibers, Patent Document 1 (Japanese Published Patent Application No. 2010-150694) discloses a liquid crystal polyester fiber characterized by having a peak full width at 18 to 22° in the equatorial direction having a full width of 3.5° or more in wide-angle X-ray diffraction measurements using a CuKα line as a source.

[0005] In addition, regarding a method for manufacturing melt anisotropic aromatic polyester fibers, Patent Document 2 (Japanese Published Patent Application No. Hei 3-227407) discloses a method for spinning melt anisotropic aromatic polyester, characterized by reducing the pressure of the vent portion to 100 to 760 mmHg and adjusting the tip pressure of the extruder to 5 to 30 kg / cm² when extruding the melt anisotropic aromatic polyester with a vent-equipped extruder, then increasing the pressure to 40 to 200 kg / cm² using a gear pump with a volumetric efficiency of 50 to 90%, and then spinning by passing through a filter. Prior art literature

[0006] Japanese Published Patent Application No. 2010-150694 Japanese Published Patent Application No. Hei 3-227407 The problem to be solved

[0007] However, in order to increase the lifespan of various applications such as electrical products, further improvement in dimensional stability compared to conventional melt-anisotropic aromatic polyester fibers is required, and thus it is necessary to improve creep characteristics, but Patent Documents 1 and 2 do not describe the improvement of creep characteristics.

[0008] Accordingly, the present invention aims to solve the above problem by providing a melt-anisotropic aromatic polyester fiber with excellent creep characteristics. means of solving the problem

[0009] The inventors of the present invention, as a result of careful consideration to achieve the above objective, discovered that when the mixing conditions in melt spinning are changed, there is a difference in the creep characteristics of the melt anisotropic aromatic polyester fiber obtained by subsequently heat-treating the spun yarn.

[0010] In addition, considering the relationship with creep characteristics, attention was paid to the crystal structure of melt-anisotropic aromatic polyester fibers, and it was found that melt-anisotropic aromatic polyester fibers with superior creep characteristics have a high degree of orthorhombicity.

[0011] As a result of further research, it was discovered that in melt spinning, by low-temperature kneading of melt anisotropic aromatic polyester with a twin-screw extruder, shear can be applied in a state of high viscosity, and it is possible to obtain a spun yarn having a more uniform microcrystalline structure. Consequently, by heat-treating such a spun yarn, molecular chains are densely packed during solid-state polymerization, and the proportion of orthorhombic, which is a denser crystal structure, can be increased, leading to the completion of the present invention.

[0012] That is, the present invention may be configured in the following embodiments.

[0013] [Mode 1]

[0014] A melt-in-the-anisotropic aromatic polyester fiber having a degree of orthorhombicity in the crystalline component of 15.0% or more (preferably 16.0% or more, more preferably 17.0% or more, even more preferably 18.0% or more, and also 25.0% or less, preferably 24.0% or less, more preferably 23.0% or less).

[0015] [Mode 2]

[0016] A melt anisotropic aromatic polyester fiber as described in Embodiment 1, wherein the density obtained by a density gradient tube is 1.4080 g / cm³ or higher.

[0017] [Mode 3]

[0018] A melt anisotropic aromatic polyester fiber as described in embodiment 1 or 2, comprising a melt anisotropic aromatic polyester having a constituent unit derived from 4-hydroxybenzoic acid in an amount of 50 mol% or more (preferably 53 mol% or more, more preferably 60 mol% or more, even more preferably 65 mol% or more, even more preferably 70 mol% or more).

[0019] [Mode 4]

[0020] A melt anisotropic aromatic polyester fiber as described in any one of embodiments 1 to 3, wherein the melting point measured by differential scanning calorimetry under a nitrogen atmosphere at a heating rate of 10 °C / min is 260 to 380 °C (preferably 270 to 360 °C, more preferably 275 to 340 °C, even more preferably 275 to 330 °C).

[0021] [Mode 5]

[0022] A fiber structure composed of at least a portion of a melt anisotropic aromatic polyester fiber described in any one of embodiments 1 to 4.

[0023] [Mode 6]

[0024] A process of melt-kneading a melt-anisotropic aromatic polyester using a twin-screw extruder at a barrel temperature from the resin feed section to the kneading section outlet below the melting point Mp0 (preferably Mp0-5°C or lower, more preferably Mp0-10°C or lower, even more preferably Mp0-15°C or lower), when the melting point Mp0 of the melt-anisotropic aromatic polyester is set to Mp0 as measured by a differential scanning calorimeter under a nitrogen atmosphere at a heating rate of 10°C / min; and

[0025] A process of obtaining spun yarn by spinning a molten blend, and

[0026] A process of heat treating the obtained spun yarn

[0027] A method for manufacturing melt anisotropic aromatic polyester fibers, comprising at least [ ].

[0028] [Mode 7]

[0029] A method for manufacturing a melt-anisotropic aromatic polyester fiber, wherein the method described in Embodiment 6 involves melt-kneading under conditions where the residence time in the kneading section of a twin-screw extruder is 10 seconds or more (preferably 15 seconds or more, more preferably 20 seconds or more).

[0030] As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural form including “at least one” unless the content clearly indicates otherwise. As used herein, the terms “and / or,” “at least one,” and “one or more” include any and all combinations of the related enumerated items.

[0031] Additionally, any combination of at least two components disclosed in the claims and / or the specification and / or the drawings is included in the present invention. In particular, any combination of two or more of the claims described in the claims is included in the present invention. Effects of the invention

[0032] The melt-anisotropic aromatic polyester fiber of the present invention has excellent creep characteristics. In addition, the manufacturing method of the present invention can produce a melt-anisotropic aromatic polyester fiber with a high degree of orthorhombicity. Brief explanation of the drawing

[0033] The invention is more clearly understood from the following description of preferred embodiments with reference to the attached drawings. However, the embodiments and drawings are for illustration and description purposes only and should not be used to define the scope of the invention. The scope of the invention is defined by the appended claims. The drawings are not necessarily drawn to a specific scale and are exaggerated to illustrate the principles of the invention. FIG. 1 is a schematic diagram illustrating a method for manufacturing a melt anisotropic aromatic polyester fiber according to one embodiment of the present invention. Specific details for implementing the invention

[0034] [Melted Anisotropic Aromatic Polyester Fiber]

[0035] The melt-anisotropic aromatic polyester fiber of the present invention comprises a melt-anisotropic aromatic polyester. The melt-anisotropic aromatic polyester is composed of constituent units derived from, for example, aromatic diols, aromatic dicarboxylic acids, aromatic hydroxycarboxylic acids, etc., and as long as the effects of the present invention are not impaired, the constituent units derived from aromatic diols, aromatic dicarboxylic acids, and aromatic hydroxycarboxylic acids are not particularly limited in their chemical composition. Furthermore, within a range that does not impede the effects of the present invention, the melt-anisotropic aromatic polyester may also include constituent units derived from aromatic diamines, aromatic hydroxyamines, or aromatic aminocarboxylic acids. For example, preferred constituent units may be those shown in Table 1.

[0036]

[0037] In the constituent units of Table 1, m is an integer from 0 to 2, and Y in the formula may be, independently, a hydrogen atom, a halogen atom (e.g., a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.), an alkyl group (e.g., a methyl group, an ethyl group, an isopropyl group, a t-butyl group, etc., alkyl groups having 1 to 4 carbon atoms), an alkoxy group (e.g., a methoxy group, an ethoxy group, an isopropoxy group, an n-butoxy group, etc.), an aryl group (e.g., a phenyl group, a naphthyl group, etc.), an aralkyl group (e.g., a benzyl group (phenylmethyl group), a phenethyl group (phenylethyl group), etc.), an aryloxy group (e.g., a phenoxy group, etc.), an aralkyloxy group (e.g., a benzyloxy group, etc.).

[0038] More preferred constituent units include the constituent units described in examples (1) to (18) shown in Tables 2, 3, and 4 below. In addition, if a constituent unit in the formula is a constituent unit capable of representing multiple structures, two or more such constituent units may be combined and used as constituent units for the polymer.

[0039]

[0040]

[0041]

[0042] In the constituent units of Tables 2, 3 and 4, n is an integer of 1 or 2, and each constituent unit n=1 or n=2 may exist alone or in combination, and Y1 and Y2 may each independently be a hydrogen atom, a halogen atom (e.g., a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.), an alkyl group (e.g., a 1 to 4 C alkyl group such as a methyl group, an ethyl group, an isopropyl group, a t-butyl group, etc.), an alkoxy group (e.g., a methoxy group, an ethoxy group, an isopropoxy group, an n-butoxy group, etc.), an aryl group (e.g., a phenyl group, a naphthyl group, etc.), an aralkyl group (e.g., a benzyl group (phenylmethyl group), a phenethyl group (phenylethyl group), etc.), an aryloxy group (e.g., a phenoxy group, etc.), an aralkyloxy group (e.g., a benzyloxy group, etc.). Among these, hydrogen atoms, chlorine atoms, bromine atoms, or methyl groups are preferred.

[0043] Also, Z can be a substituent represented by the following formula.

[0044] [Chemical Formula 1]

[0045]

[0046] The melt anisotropic aromatic polyester may preferably be a combination having a naphthalene backbone as a constituent unit. It is particularly preferable to include both a constituent unit (A) derived from hydroxybenzoic acid and a constituent unit (B) derived from hydroxynaphthoic acid. For example, the following formula (A) may be used as the constituent unit (A) and the following formula (B) may be used as the constituent unit (B). In order to improve melt moldability, the ratio of the constituent unit (A) to the constituent unit (B) may preferably be in the range of 9 / 1 to 1 / 1, more preferably 7 / 1 to 1 / 1, and even more preferably 5 / 1 to 1 / 1.

[0047] [Chemical Formula 2]

[0048]

[0049] [Chemical Formula 3]

[0050]

[0051] In addition, the sum of the constituent units of (A) and (B) may, for example, be 65 mol% or more with respect to the total constituent units, more preferably 70 mol% or more, and even more preferably 80 mol% or more. Among the polymers, a melt anisotropic aromatic polyester in which the constituent units of (B) are 4 to 45 mol% is particularly preferred.

[0052] The melted anisotropic aromatic polyester may contain constituent units derived from 4-hydroxybenzoic acid, preferably 50 mol% or more, more preferably 53 mol% or more, even more preferably 60 mol% or more, even more preferably 65 mol% or more, and particularly preferably 70 mol% or more. The upper limit of the content of constituent units derived from 4-hydroxybenzoic acid in the melted anisotropic aromatic polyester is not particularly limited, but, for example, it may be 90 mol% or less, preferably 88 mol% or less, and more preferably 85 mol% or less.

[0053] The melting point of the molten anisotropic aromatic polyester used in the present invention (hereinafter referred to as Mp0) is preferably in the range of 250 to 380 °C, more preferably 255 to 370 °C, even more preferably 260 to 360 °C, and even more preferably 260 to 330 °C. In this specification, the melting point is the temperature of the main absorption peak observed by measuring with a differential scanning calorimeter (DSC) in accordance with the JIS K 7121 test method. Specifically, 4 to 6 mg of the sample is taken into a DSC device and sealed in an aluminum pan, and nitrogen is flowed as a carrier gas at a flow rate of 200 mL / min, and the endothermic peak is measured when the temperature is raised from room temperature (e.g., 25 °C) to 10 °C / min. If a clear peak does not appear in the 1st run of the DSC measurement depending on the type of polymer, the temperature can be raised at a rate of 50 ℃ / min to a temperature 50 ℃ higher than the expected flow temperature, completely melted at that temperature for 3 minutes, then lowered to 50 ℃ at a rate of 80 ℃ / min, and then the endothermic peak can be measured at a rate of 10 ℃ / min.

[0054] In addition, the melt-anisotropic aromatic polyester fiber may include thermoplastic polymers such as polyethylene terephthalate, modified polyethylene terephthalate, polyolefin, polycarbonate, polyamide, polyphenylene sulfide, polyetheretherketone, and fluoropolymer, to the extent that it does not impede the effects of the present invention. Furthermore, it may include various additives such as inorganic materials such as titanium oxide, kaolin, silica, and barium oxide, carbon black, coloring agents such as dyes or pigments, antioxidants, ultraviolet absorbers, and light stabilizers.

[0055] The melt-anisotropic aromatic polyester fiber of the present invention may contain 50 weight% or more of melt-anisotropic aromatic polyester, preferably 80 weight% or more, more preferably 90 weight% or more, even more preferably 95 weight% or more, and even more preferably 99.9 weight% or more.

[0056] The melt-anisotropic aromatic polyester fiber of the present invention has a degree of orthorhombicity of 15.0% or more in its crystal components. Although melt-anisotropic aromatic polyesters have crystal components such as orthorhombic or hexagonal systems, since orthorhombic has a crystal structure in which molecular chains are packed more densely, melt-anisotropic aromatic polyester fibers that not only increase the degree of crystallinity or orientation but also increase the proportion of orthorhombic in their crystal components have excellent creep properties due to their dense crystal structure. The degree of orthorhombicity may preferably be 16.0% or more, more preferably 17.0% or more, and even more preferably 18.0% or more. In addition, the degree of orthorhombicity may be, for example, 25.0% or less, preferably 24.0% or less, and more preferably 23.0% or less. In this specification, the degree of orthorhombicity of a melt anisotropic aromatic polyester fiber is calculated from diffraction peaks originating from orthorhombic and hexagonal X-ray diffraction profiles obtained by wide-angle X-ray diffraction measurement (e.g., diffraction peaks appearing around the diffraction angle 2θ = 19 to 21°, etc.) and is a value measured by the method described in the examples below.

[0057] The melt-anisotropic aromatic polyester fiber of the present invention has a high density because the proportion of orthorhombic molecules, in which molecular chains are densely packed, is high, and for example, the density obtained by a density gradient may be 1.4080 g / cm³ or higher. The upper limit of the density is not particularly limited and may vary depending on the composition of the melt-anisotropic aromatic polyester, but for example, it may be 1.4200 g / cm³ or lower. In this specification, the density of the melt-anisotropic aromatic polyester fiber is a value measured by the method described in the examples below.

[0058] The melt anisotropic aromatic polyester fiber of the present invention may have a melting point of 260 to 380 °C, preferably 270 to 360 °C, more preferably 275 to 340 °C, and even more preferably 275 to 330 °C. The melting point of the melt anisotropic aromatic polyester fiber increases from the melting point (Mp) of the spun yarn due to solid-state polymerization. Furthermore, the melting point of the melt anisotropic aromatic polyester fiber is a value measured by the method described in the examples described below.

[0059] The melt-anisotropic aromatic polyester fiber of the present invention may have a tensile strength of 20 cN / dtex or higher, preferably 24 cN / dtex or higher, and more preferably 25 cN / dtex or higher. In addition, the upper limit of the tensile strength is not particularly limited, but may be, for example, about 40 cN / dtex. The tensile strength of the melt-anisotropic aromatic polyester fiber is a value measured by the method described in the examples described below.

[0060] The melt anisotropic aromatic polyester fiber of the present invention may have a time until the fiber breaks in a creep test by the method described in the examples below of 30 hours or more, preferably 60 hours or more, and more preferably 68 hours or more.

[0061] The melt-anisotropic aromatic polyester fiber of the present invention may appropriately select the short fiber fineness according to the application, etc. For example, the short fiber fineness may be 50 dtex or less, preferably 15 dtex or less, and more preferably 10 dtex or less. However, from the perspective of responding to miniaturization for applications such as electrical products, it is preferable to have a fine fineness, for example, 7 dtex or less. In addition, the lower limit of the short fiber fineness is not particularly limited, but for example, it may be about 0.01 dtex. The short fiber fineness is a value measured by the method described in the examples described below.

[0062] The melt anisotropic aromatic polyester fiber of the present invention may be a monofilament or a multifilament. In the case of a multifilament, the number of filaments can be appropriately selected according to the application, etc. For example, the number of filaments may be 2 to 5,000, preferably 3 to 4,000, and more preferably 5 to 3,000.

[0063] The melt-anisotropic aromatic polyester fiber of the present invention may have a total fineness appropriately selected according to the application, etc. For example, the total fineness may be 50,000 dtex or less, preferably 10,000 dtex or less, more preferably 2,000 dtex or less, and even more preferably 1,000 dtex or less. In addition, the lower limit of the total fineness is not particularly limited, but for example, it may be about 1 dtex.

[0064] [Method for manufacturing melt-anisotropic aromatic polyester fibers]

[0065] The method for manufacturing a melt anisotropic aromatic polyester fiber of the present invention is,

[0066] A process of melt-kneading a melt-anisotropic aromatic polyester using a twin-screw extruder at a barrel temperature from the resin feed section to the kneading section outlet at a temperature below the melting point Mp0, wherein the melting point Mp0 of the melt-anisotropic aromatic polyester is determined by differential scanning calorimetry under a nitrogen atmosphere at a heating rate of 10 ℃ / min; and

[0067] A process of obtaining spun yarn by spinning a molten blend, and

[0068] At least a process for heat treating the obtained spun yarn is provided.

[0069] In the present invention, by using a twin-screw extruder to improve the kneading properties of the molten anisotropic aromatic polyester, and by setting the kneading section within the twin-screw extruder to a low temperature below the melting point and kneading in a state of high viscosity, it is possible to efficiently impart shear to the molten anisotropic aromatic polyester. It should be noted that this is a temperature condition opposite to the usual one with respect to the melting point of the resin, as it is common practice to promote melting by heating above the melting point of the input resin.

[0070] In addition, perhaps because spinning a molten mixture that has been sheared by mixing at low temperatures in this manner allows for obtaining a spun yarn with a more uniform microcrystalline structure, molecular chains in this spun yarn are densely packed during solid-state polymerization by heat treatment, and the proportion of orthorhombic, which is a denser crystal structure, can be increased.

[0071] In addition, by applying shear through mixing at a low temperature, melting can be promoted compared to conventional melt mixing conditions, perhaps because more mechanical energy can be applied than thermal energy compared to heating above the melting point of the resin as in the conventional method. As a result, in addition to forming a crystal structure, it is also possible to reduce the residue of unmelted material, so the filter formed to remove foreign substances is less likely to clog, and the occurrence of yarn breakage during spinning can be suppressed.

[0072] In addition, although it is generally known that a single-screw extruder is used in the melt spinning method, if the extruder temperature is set below the melting point as described above, the resin cannot be spun stably due to poor jamming, pressure fluctuations, and increased torque. This is thought to be because, compared to a twin-screw extruder which melts the resin through heat generation caused by high shear, the contribution of heat transfer from the extruder barrel during melting is significant in a single-screw extruder. Therefore, the same effect cannot be obtained by using a single-screw extruder in the present invention.

[0073] A method for manufacturing molten anisotropic aromatic polyester fibers is described below with reference to FIG. 1. FIG. 1 is a schematic diagram showing the internal configuration from the side of a twin-screw extruder (100) used for manufacturing molten anisotropic aromatic polyester fibers according to one embodiment of the present invention. As shown in FIG. 1, the twin-screw extruder (100) is equipped with a hopper (11) for feeding molten anisotropic aromatic polyester, a barrel (12), a screw (13) rotating within the barrel (12), and a vent (14), and has a resin feed section (21), a mixing section (22), and a transport section (23) extending from the upstream side to the downstream side within the barrel (12). The resin feed section (21), the mixing section (22), and the transport section (23) each have screw elements (13a, 13b, 13c) of the screw (13). In addition, the screw (13) (screw element (13a, 13b, 13c)) represents one of the screws of the twin extruder (100). FIG. 1 is illustrated in a simple structure to explain the method for manufacturing a melt anisotropic aromatic polyester fiber of the present invention, but various equipment may be installed as needed, and equipment generally used in twin extruders may be provided in addition to the equipment shown.

[0074] In FIG. 1, the solid molten anisotropic aromatic polyester fed from the hopper (11) is transported in the X direction, which is the direction of travel, by the rotation of the screw (13) within the barrel (12), and is heated by a known heating means, such as a heater installed in the barrel (12). In addition to the heat transfer from the heating means, the solid molten anisotropic aromatic polyester is melted as it travels in the X direction by applying shear between the inner wall of the barrel (12) and the screw (13) or between the screws (13). Furthermore, the molten anisotropic aromatic polyester may be fed into a twin-screw extruder (100) as a resin composition comprising the thermoplastic polymer described above and various additives.

[0075] In the resin feed section (21), the solid molten anisotropic aromatic polyester supplied from the hopper (11) is pressed and solidified in a solid state by the rotation of the screw (13) and moves in the X direction, and can be gradually melted by the heat transfer by the heating means of the barrel (12) and the shearing applied by the rotation of the screw (13). For example, a full-flight screw is used as the screw element (13a) used in the resin feed section (21).

[0076] In the mixing section (22), the melting of the molten anisotropic aromatic polyester containing the solid transported from the resin feed section (21) can be promoted by mixing using a shear-improving screw element, such as a kneading disc, as the screw element (13b). In FIG. 1, the mixing section (22) is provided at one point, but the mixing section may be provided at multiple points.

[0077] In the transport section (23), the viscosity can be adjusted when transporting the molten mixture obtained in the mixing section (22) to the spinning head. For example, a full-flight screw is used as the screw element (13c) used in the transport section (23).

[0078] In the present invention, by setting the temperature of the resin feed section (21) and the mixing section (22) within the barrel (12) to a low temperature below the melting point Mp0 of the molten anisotropic aromatic polyester fed into the twin-screw extruder (100), it is possible to efficiently apply shear to the molten anisotropic aromatic polyester in a high-viscosity state. The temperature of the barrel (12) from the resin feed section (21) to the outlet of the mixing section (22) may preferably be Mp0-5°C or lower, more preferably Mp0-10°C or lower, and even more preferably Mp0-15°C or lower. In addition, from the perspective of promoting melting by heating, it may be Mp0-100°C or higher, preferably Mp0-90°C or higher, and more preferably Mp0-80°C or higher. In the manufacturing method of the present invention, the barrel temperature from the resin feed section to the mixing section outlet refers to the barrel temperature up to the outlet of the downstream mixing section adjacent to the transport section, in cases where there are multiple mixing sections.

[0079] The heating means installed in the barrel (12) may be controlled to have different temperatures in each region in the direction of travel from the upstream side to the downstream side, and it is preferable to adjust the temperature of the barrel (12) from the resin feed section (21) to the mixing section (22) outlet so that it gradually increases within the above temperature range.

[0080] In the present invention, the temperature of the resin feed section (21) and the mixing section (22) within the barrel (12) is adjusted to within the above temperature range, and the temperature of the barrel (12) of the subsequent transport section (23) may be Mp0 or higher, preferably Mp0+10°C or higher, more preferably Mp0+20°C or higher, from the perspective of adjusting viscosity during spinning. Also, from the perspective of suppressing the decomposition of the melt anisotropic aromatic polyester, it may be 400°C or lower, preferably 370°C or lower, more preferably 350°C or lower.

[0081] The residence time in the mixing section (22) may be 10 seconds or more, preferably 15 seconds or more, more preferably 20 seconds or more, from the perspective of efficiently applying shear to the molten anisotropic aromatic polyester and improving spinnability. Also, from the perspective of suppressing the deterioration of the molten anisotropic aromatic polyester, it may be 300 seconds or less, preferably 180 seconds or less, more preferably 130 seconds or less. The residence time in the mixing section can be calculated using the following formula based on the volume of the mixing section and the discharge amount.

[0082] (Void in barrel [cm³]) = (Volume in mixing section barrel [cm³]) - (Volume of mixing section screw [cm³])

[0083] (Mixing section residence time [s]) = (Void in barrel [cm³]) / (Volumetric discharge rate [cm³ / s])

[0084] Depending on the type of molten anisotropic aromatic polyester or spinning conditions, the capacity, distribution, and arrangement of the resin feed section, mixing section, and transport section, as well as the shape of the screws and the gaps between the screws, may be appropriately designed. Additionally, in addition to screw elements such as full-flight screws or kneading discs, screw elements that reverse the direction of travel from the upstream side to the downstream side, such as back-kneading discs, may be installed. Furthermore, sealing may be used on the elements at the outlet of the mixing section to efficiently retain the resin in the mixing section or to improve sealing performance in the upstream section of the vent.

[0085] In the twin extruder (100), since there may be bubbles during melt mixing due to air entrapment, for example, it is preferable to degas by installing a vent (14) in the twin extruder (100) and connecting a pressure reducing pump, etc., to reduce the pressure inside the twin extruder (100). For example, the vacuum level may be 100 kPa or less in absolute pressure, preferably 80 kPa or less, and more preferably 60 kPa or less.

[0086] The molten mixture obtained by melting and mixing in a twin-screw extruder (100) is then metered from the transport unit (23) to a gear pump (not shown) and transported to a spinning head. To avoid the mixing of foreign substances, such as unmelted material contained in the molten mixture, a filter may be installed before or after the gear pump after being transported from the twin-screw extruder (100). In the present invention, since the remaining unmelted material can be reduced by melting and mixing in the twin-screw extruder, the filter is less likely to clog, and spinning can be stabilized.

[0087] After being transported to a spinning head, a molten blend is discharged through a nozzle at a predetermined spinning temperature, and the obtained yarn is wound by a godet roller or the like to produce a spun yarn of molten anisotropic aromatic polyester fiber. The spinning temperature (spinning die temperature) may be, for example, Mp0-30 to Mp0+60 ℃ with respect to the melting point Mp0 of the molten anisotropic aromatic polyester, preferably Mp0-25 ℃ to Mp0+50 ℃, and more preferably Mp0-20 ℃ to Mp0+45 ℃. In addition, the spinning temperature may be between the barrel temperature of the mixing section + 10°C and the barrel temperature of the mixing section + 120°C, preferably between the barrel temperature of the mixing section + 15°C and the barrel temperature of the mixing section + 100°C, more preferably between the barrel temperature of the mixing section + 20°C and the barrel temperature of the mixing section + 90°C, and even more preferably between the barrel temperature of the mixing section + 30°C and the barrel temperature of the mixing section + 80°C. If the spinning temperature (spinning die temperature) is below the above upper limit, resin degradation near the die can be suppressed, and it is difficult for processability defects caused by single filaments or yellowing of the product to occur.

[0088] Because the spun yarn forms a more uniform microcrystalline structure, heat treatment of the spun yarn promotes solid-state polymerization of the melt-anisotropic aromatic polyester, and as the melting point rises from the melting point (Mp) of the spun yarn, the degree of orthogonality in the fiber after heat treatment can be increased. In the heat treatment process, the method of heat treatment is not particularly limited; for example, it may be a batch heat treatment or a continuous heat treatment by conveying. In addition, the melting point (Mp) of the spun yarn can be measured by the same method as the melting point of the melt-anisotropic aromatic polyester fiber.

[0089] For example, in the heat treatment of a batch process, the heat treatment may be performed in a packaged state on a bobbin, a spool, or a fiber bundle, for example; however, it is preferable to perform the treatment in a packaged state as this simplifies the equipment and improves productivity. The bobbin needs to withstand the temperature of solid-state polymerization, and it is preferable that it be made of a metal such as aluminum, brass, iron, or stainless steel.

[0090] In the case of continuous heat treatment by conveying, the conveying method may be carried out using either contact conveying (e.g., a conveyor system, a support roll system, or a heat treatment method on heated rollers) or non-contact conveying (roll-to-roll system). Furthermore, the processing path does not have to be a straight line, and heat treatment may be performed by appropriately changing the length, angle, curvature, etc., of the processing path by placing return rollers or guides within the device.

[0091] For the heat treatment process, known methods may be used, such as atmospheric heating or contact heating. As the atmosphere, air, an inert gas (e.g., nitrogen, argon), or a combination thereof is preferably used. Furthermore, there is no problem at all if the heat treatment is performed under reduced pressure.

[0092] In the heat treatment process, the heat treatment temperature may be 250 to 350 ℃, preferably 255 to 320 ℃, more preferably 260 to 315 ℃, and more preferably 280 to 310 ℃. In addition, the heat treatment temperature may be below the melting point (Mp) of the spun yarn provided to the heat treatment process to prevent melting, for example, in the range of 250 to 350 ℃, it may be Mp-50 ℃ or higher and less than Mp ℃, preferably Mp-40 ℃ or higher and less than Mp ℃, and more preferably Mp-30 ℃ or higher and less than Mp ℃. In the heat treatment process, since the melting point of the melt anisotropic aromatic polyester fiber increases with the progress of solid-state polymerization, the initial heat treatment temperature in the heat treatment process may be lower than the melting point (Mp) of the spun yarn, and from the perspective of efficient strength improvement, the heat treatment temperature may be increased stepwise according to the progress of solid-state polymerization, and heat treatment may be performed at a temperature exceeding the melting point (melting point of the spun yarn) at the time of providing the heat treatment process.

[0093] The heat treatment time of the heat treatment process can be appropriately set according to the heat treatment method or heat treatment temperature. For example, it can be set from a range of 15 minutes to 30 hours, preferably 2 to 24 hours, more preferably 3 to 20 hours, and the heat treatment time here refers to the holding time at a predetermined heat treatment temperature (e.g., maximum temperature).

[0094] In the method for manufacturing a melt-anisotropic aromatic polyester fiber of the present invention, for example, a known emulsion or a fusion inhibitor may be applied before the heat treatment process to improve the fiber's cohesiveness or to prevent fusion during heat treatment.

[0095] [Fiber structure]

[0096] The melt-anisotropic aromatic polyester fiber of the present invention can be used for various purposes as a fiber structure comprising at least a portion thereof. The fiber structure comprising the melt-anisotropic aromatic polyester fiber of the present invention can be used in any fiber form, such as staple fiber, short-cut fiber, filament yarn, spun yarn, cord-shaped material, rope, etc. In addition, it can be used as various fabrics such as nonwoven fabrics, woven fabrics, and knitted fabrics using the melt-anisotropic aromatic polyester fiber. Such fibers or fabrics can be manufactured using the melt-anisotropic aromatic polyester fiber by a known method.

[0097] The fiber structure of the present invention may be a combination of melt-anisotropic aromatic polyester fibers and other fibers, provided that it does not impede the effects of the present invention. For example, a composite fiber using melt-anisotropic aromatic polyester fibers and other fibers (e.g., a blended yarn in which melt-anisotropic aromatic polyester fibers and other fibers are blended) may be used. In addition, a composite fabric using melt-anisotropic aromatic polyester fibers and other fibers may be used (e.g., a blended fabric in which melt-anisotropic aromatic polyester fibers and other fibers are blended, or a laminate of a fabric made of melt-anisotropic aromatic polyester fibers and a fabric made of other fibers).

[0098] The melt-anisotropic aromatic polyester fiber of the present invention can be used in the form of various fiber structures for various applications, such as general industrial materials, civil engineering and construction materials, various reinforcing materials, electrical and electronic component materials, and various fiber products. For example, it can be used in tension members (electric wires, optical fibers, umbilical cables, heater wires, cords of various electrical products such as earphone cords, etc.), sailcloth, ropes (marine, mountaineering, cranes, yachts, tags, etc.), ropes, land nets, slings, lifelines, fishing lines, sewing threads, netting cords, fishing nets, kite strings, geogrids, protective gloves, ripstop for protective clothing and outdoor medical use, rider suits, sports rackets, guts, medical catheter reinforcements, suture threads, screen threads, filters, foam for printed circuit boards, mesh-type conveyor belts, papermaking belts, dryer canvas, airships, balloons, airbags, speaker cones, reinforcements for various hoses and pipes, and reinforcements for rubber and plastics such as tires and conveyor belts, etc. In particular, the melt-anisotropic aromatic polyester fiber of the present invention can be preferably used as a tension member because it has excellent creep characteristics.

[0099] Examples

[0100] The present invention will be described in more detail below based on examples, but the present invention is not limited thereto. In addition, in the following examples and comparative examples, various physical properties were measured by the following methods.

[0101] (Melting point of resin chips (granular molded bodies) and fibers)

[0102] In accordance with JIS K 7121, measurements were taken using a differential scanning calorimeter (DSC; "DSC60A Plus" manufactured by Shimadzu Corporation), and the temperature of the observed main absorption peak was set as the melting point. Specifically, 4 to 6 mg of the sample was placed in an aluminum pan using the above-mentioned DSC apparatus, and nitrogen was flowed as a carrier gas at a flow rate of 200 mL / min. The endothermic peak derived from the melting anisotropic aromatic polyester was measured when the temperature was increased from 25 ℃ to 10 ℃ / min.

[0103] (pressure increase)

[0104] 50 kg of melt-mixed anisotropic aromatic polyester, melt-mixed under each condition in a twin-screw extruder, was transported and passed through a container equipped with a metal nonwoven filter of size φ76 with a scale interval of 30 μm, and the pressure was monitored using a resin pressure gauge GC75 manufactured by Nagano Keiki Co., Ltd. installed in the container, and the amount of pressure increase before and after passing was recorded.

[0105] (Radioactive)

[0106] A melted anisotropic aromatic polyester was extruded, and a spinning test was conducted for 3 days after winding was started, the number of single filaments generated at that time was counted, and evaluated according to the following criteria.

[0107] ◎ : Single injection frequency 0 times / day

[0108] ○ : Frequency of single injections is greater than 0 times / day and less than 0.7 times / day

[0109] △ : Single injection frequency 0.7 times / day or more, less than 2.0 times / day

[0110] × : Single injection frequency 2.0 times / day or more

[0111] (Sabangjeonghwado)

[0112] A molten anisotropic aromatic polyester fiber was mounted in a fiber holder, and X-rays were incident in a direction orthogonal to the fiber axis using the transmission method under the following measurement conditions, and wide-angle X-ray diffraction (WAXD) measurements were performed.

[0113] Measuring device: Bruker "D8 Discover IμS"

[0114] Detector: 2D PSPC·VANTEC-500

[0115] X Source: Cu

[0116] Current: 1 mA

[0117] Voltage: 50 kV

[0118] Exposure time: 10 minutes

[0119] Collimator diameter: 0.5 mm

[0120] Camera length: 17 cm

[0121] Detector position (2θ): 20°

[0122] Sample position (ω): 10°

[0123] Angle of elevation (Ψ): 90°

[0124] Measurement temperature: Room temperature (approx. 25 ℃)

[0125] Under the following conditions, an X-ray diffraction profile was obtained with the horizontal axis being the diffraction angle (2θ) and the vertical axis being the intensity.

[0126] Integration range: 2θ = 5 ∼ 35°, γ (azimuth) = 250 ∼ 290°

[0127] Step width: 0.05° (diffraction angle)

[0128] In the obtained X-ray diffraction profile, a baseline was established by connecting the values ​​of 2θ = 5° and 35° with a straight line. Based on this newly established baseline, the difference in intensity along the vertical axis from the measured data to the baseline was converted into profile data with the new intensity.

[0129] For the profile data after baseline correction, a pseudopoite function (ratio of Lorentz function: α=0) was used to fit the non-finite peak with peak height, peak top position, σ, and asymmetry parameter as variables. At this time, the initial value of the peak top position of the fitting function was set to approximately 20.6°. The peak area of ​​this fitting function was calculated as the non-finite (D).

[0130] For peaks A (peak top position around 19°), B (peak top position around 20.5°), and C (peak top position around 27°) of the profile data after baseline correction, the determination peaks were fitted using the following function with peak height, peak top position, and σ as variables. All determination peaks were made symmetric.

[0131] Peak A: Pseudopoite function (α=1)

[0132] Peak B: Pseudopoite function (α=0)

[0133] Peak C: Pseudopoite function (α=0.5)

[0134] In addition, fitting was performed using the least squares method, including the fitting function of the previously obtained non-normal peak, so that the difference between the sum of all fitting functions and the profile data after baseline correction was minimized. The peak areas of these fitting functions were calculated as the determined amounts (A), (B), and (C), respectively.

[0135] Using the amount of determination of peak A originating from the hexagon (A) and the amount of determination of peak B originating from the orthorhombic (B), the degree of orthorhombicity was calculated from the following equation.

[0136] Orthorhombicity (%) = (B) / {(A)+(B)}×100

[0137] (Fiber density)

[0138] Density measurements were performed in reference to the density gradient method (JIS L 1013: 2010 8.17.2). To compare slight density differences caused by the packing of fibers due to erosion, the average of five measurements of each sample was calculated by rounding to four decimal places.

[0139] (Total fiber fineness, single fiber fineness)

[0140] Based on the JIS L 1013:2010 8.3.1 A method, 10 m of molten anisotropic aromatic polyester fiber was taken using the "Wrap Reel by Motor Driven" measuring instrument manufactured by Daiei Kagaku Seiki Co., Ltd., and the weight (g) was multiplied by 1000 to perform 3 measurements per level, and the average of the 3 measurements was taken as the total fineness (dtex) of the obtained molten anisotropic aromatic polyester fiber. In addition, the quotient obtained by dividing this value by the number of filaments was taken as the staple fiber fineness (dtex).

[0141] (tensile strength)

[0142] Referring to JIS L 1013:2010 8.5.1, five tensile tests were performed on one sample using the tensile strength measuring instrument “TENSORAPID5” manufactured by USTER Technologies under conditions of a test length of 30 cm, a tensile speed of 15 cm / min, and an initial load of 0.33 g / dtex, and the tensile strength (cN / dtex) was calculated by dividing the average tensile strength (cN) of the five tests by the total denier (dtex) measured by the method described above.

[0143] (Creep trait)

[0144] Using the creep tester "525-R CREEP TESTER" manufactured by Maize Testing Machine Co., Ltd., measurements were started from the point when a load of 0.18 N / dtex was applied to a fiber with a test length of 300 mm at a measurement temperature of 20 ℃, and the time until the fiber broke was measured. Measurements were performed three times per sample, and the average value was calculated.

[0145] [Example 1]

[0146] Chips (granular molded bodies) of a molten anisotropic aromatic polyester (Mp0: 278 °C) having 73 / 27 (mol%) of a constituent unit (A) derived from 4-hydroxybenzoic acid and a constituent unit (B) derived from 6-hydroxy-2-naphthoic acid were hot-air dried at 120 °C for 4 hours or more. Afterwards, the chips were fed into a twin-screw extruder with a void volume in the barrel of the mixing section set to 14.7 cm³, and melt-mixed by setting the barrel temperature from the resin feed section to the mixing section outlet to 260 °C and the barrel temperature of the transport section downstream from the mixing section outlet to 325 °C. At that time, the residence time in the mixing section was adjusted to 21 seconds. At this time, a pressure reduction pump was connected via a metal pipe through the vent section of the twin-screw extruder, and the pressure in the polymer-non-filled space within the twin-screw extruder was reduced to 30 kPa. Subsequently, the molten mixture was supplied from the twin-screw extruder to the spinning head while being metered by a gear pump. The spinning head was equipped with a spinneret with a hole diameter of 0.10 mmφ and 100 holes, the spinneret temperature was set to 320 °C, and the molten mixture was discharged at a volumetric discharge rate of 42.0 cm³ / min to obtain a spun yarn of 560 dtex / 100f. Afterward, the obtained spun yarn was heat-treated at 275 °C for 16 hours under a nitrogen atmosphere to obtain a heat-treated yarn of melt-anisotropic aromatic polyester fiber. The analysis results of the obtained melt-anisotropic aromatic polyester fiber are shown in Table 5.

[0147] [Example 2]

[0148] A melt-anisotropic aromatic polyester fiber was obtained in the same manner as in Example 1, except that the void volume inside the barrel of the mixing section was 44.1 cm³, the barrel temperature from the resin feed section to the mixing section outlet was 240 ℃, the volumetric discharge rate was 126.1 cm³ / min, and the number of holes in the spinneret was 300.

[0149] [Example 3]

[0150] A melt anisotropic aromatic polyester fiber was obtained in the same manner as in Example 1, except that the barrel temperature from the resin feed section to the mixing section outlet was set to 220 ℃.

[0151] [Example 4]

[0152] A melt anisotropic aromatic polyester fiber was obtained in the same manner as in Example 1, except that the barrel temperature from the resin feed section to the mixing section outlet was set to 200°C.

[0153] [Example 5]

[0154] A melt-anisotropic aromatic polyester fiber was obtained in the same manner as in Example 1, except that the void volume inside the barrel of the mixing section was 29.4 cm³, the barrel temperature from the resin feed section to the mixing section outlet was 230 ℃, the volume discharge rate was 30.2 cm³ / min, and the residence time in the mixing section was 58.5 seconds.

[0155] [Example 6]

[0156] A melt-anisotropic aromatic polyester fiber was obtained in the same manner as in Example 1, except that the barrel temperature from the resin feed section to the mixing section outlet was 250 ℃, the volumetric discharge rate was 7.0 cm³ / min, the residence time in the mixing section was 126 seconds, and the number of holes in the spinneret was 10.

[0157] [Example 7]

[0158] A melt anisotropic aromatic polyester fiber was obtained in the same manner as in Example 1, except that the barrel temperature from the resin feed section to the mixing section outlet was 230 ℃, the volumetric discharge rate was 58.8 cm³ / min, and the residence time in the mixing section was 15 seconds.

[0159] [Example 8]

[0160] A melt anisotropic aromatic polyester fiber was obtained in the same manner as in Example 1, except that the volumetric discharge rate was 96.9 cm³ / min and the residence time in the mixing section was 9.1 seconds.

[0161] [Example 9]

[0162] Chips (granular molded bodies) of a molten anisotropic aromatic polyester (Mp0: 311 °C) having 78 / 22 (mol%) of a constituent unit (A) derived from 4-hydroxybenzoic acid and a constituent unit (B) derived from 6-hydroxy-2-naphthoic acid were hot-air dried at 120 °C for 4 hours or more. Afterwards, the chips were fed into a twin-screw extruder with a void volume in the barrel of the mixing section set to 14.7 cm³, and melt-mixed by setting the barrel temperature from the resin feed section to the mixing section outlet to 270 °C and the barrel temperature of the transport section downstream from the mixing section outlet to 340 °C. At that time, the residence time in the mixing section was adjusted to 21 seconds. At this time, a pressure reduction pump was connected via a metal pipe through the vent section of the twin-screw extruder, and the pressure in the polymer-non-filled space within the twin-screw extruder was reduced to 30 kPa. Subsequently, the molten mixture was supplied from the twin-screw extruder to the spinning head while being metered by a gear pump. The spinning head was equipped with a spinneret having a hole diameter of 0.10 mmφ and 100 holes, the spinneret temperature was set to 340 °C, and the molten mixture was discharged at a volumetric discharge rate of 42.0 cm³ / min to obtain a spun yarn of 560 dtex / 100f. Afterward, the obtained spun yarn was heat-treated at 280 °C for 16 hours under a nitrogen atmosphere to obtain a heat-treated yarn of melt-anisotropic aromatic polyester fiber.

[0163] [Comparative Example 1]

[0164] A melt-anisotropic aromatic polyester fiber was obtained in the same manner as in Example 1, except that a φ50 mm single-screw extruder without a vent was used and the barrel temperature excluding the resin feed section was set to 320 ℃.

[0165] [Comparative Example 2]

[0166] A melt anisotropic aromatic polyester fiber was obtained in the same manner as in Example 1, except that the barrel temperature from the resin feed section to the mixing section outlet was set to 300 ℃.

[0167] [Comparative Example 3]

[0168] A melt anisotropic aromatic polyester fiber was obtained in the same manner as in Example 1, except that the barrel temperature from the resin feed section to the mixing section outlet was set to 285 ℃.

[0169] [Comparative Example 4]

[0170] A melt-anisotropic aromatic polyester fiber was obtained in the same manner as in Example 9, except that a φ50 mm single-screw extruder without a vent was used and the barrel temperature excluding the resin feed section was set to 350 ℃.

[0171]

[0172] As shown in Table 5, in Examples 1 to 9, melt-kneading was performed by setting the barrel temperature from the resin feed section to the kneading section outlet of the twin-screw extruder to a specific low temperature condition, so melt-anisotropic aromatic polyester fibers with a high degree of orthorhombicity could be obtained. Therefore, the melt-anisotropic aromatic polyester fibers of Examples 1 to 9 have excellent creep characteristics.

[0173] Meanwhile, in Comparative Examples 1 and 4, a single-screw extruder was used, and since the barrel temperature from the resin feed section to the mixing section outlet was high, the degree of orthorhombicity could not be increased. Also, in Comparative Examples 2 and 3, although a twin-screw extruder was used, the degree of orthorhombicity could not be increased because the barrel temperature from the resin feed section to the mixing section outlet was high. Therefore, the creep characteristics of the melt anisotropic aromatic polyester fibers of Comparative Examples 1 to 4 were inferior to those of Examples 1 to 9.

[0174] Industrial applicability

[0175] The melt-anisotropic aromatic polyester fiber of the present invention can be used for various purposes, such as general industrial materials, civil engineering and construction materials, various reinforcing materials, electrical and electronic component materials, and various fiber products, and, for example, can be used as a tension member.

[0176] As described above, preferred embodiments of the present invention have been explained with reference to the drawings; however, various additions, changes, or deletions are possible without departing from the spirit of the present invention, and such additions, changes, or deletions are also included within the scope of the present invention. Explanation of the symbols

[0177] 100: Twin-screw extruder 11 : Hopper 12 : Barrel 13 : Screw 13a, 13b, 13c: Screw element 14 : Vent 21 : Suji feed 22 : Mixed Training Unit 23 : Transportation Department X : Flow direction

Claims

Claim 1 A method for manufacturing a melt anisotropic aromatic polyester fiber, comprising at least the following steps: a process of melting and kneading the melt anisotropic aromatic polyester using a twin-screw extruder at a barrel temperature from the resin feed section to the kneading section outlet at a temperature below the melting point Mp0, when the melting point Mp0 of the melt anisotropic aromatic polyester is measured by a differential scanning calorimeter under a nitrogen atmosphere at a heating rate of 10 ℃ / min; a process of spinning the melted and kneaded product to obtain a spun yarn; and a process of heat treating the obtained spun yarn. Claim 2 A method for manufacturing melt anisotropic aromatic polyester fibers according to claim 1, wherein the melt mixing is performed under conditions where the residence time in the mixing section of a twin-screw extruder is 10 seconds or more. Claim 3 A melt-anisotropic aromatic polyester fiber produced by the method of claim 1, having an orthorhombic degree of 15.0% or more in the crystalline component. Claim 4 In claim 3, a melt anisotropic aromatic polyester fiber having a density of 1.4080 g / cm³ or higher as determined by a density gradient. Claim 5 A melt-anisotropic aromatic polyester fiber comprising a melt-anisotropic aromatic polyester having 50 mol% or more of a constituent unit derived from 4-hydroxybenzoic acid, in claim 3 or 4. Claim 6 In claim 3 or 4, a melt anisotropic aromatic polyester fiber having a melting point of 260 to 380°C as measured by a differential scanning calorimeter under a nitrogen atmosphere at a heating rate of 10°C / min. Claim 7 A fiber structure composed of at least a portion of the melt anisotropic aromatic polyester fibers described in claim 3 or 4.

Images