Liquid crystalline polyester fibers and process for their production

Abstract

The present application provides a liquid crystal polyester fiber having excellent liquid absorption. The liquid crystal polyester fiber has a metal salt of a fatty acid having 9 or more carbon atoms attached to the surface of the fiber. For example, the arithmetic mean height Sa of the fiber surface of the liquid crystal polyester fiber, measured according to ISO 25178, can be 7.5 nm or less. In addition, the strength of the liquid crystal polyester fiber can be 20 cN / dtex or more. In addition, the attached amount of the metal salt of the fatty acid of the liquid crystal polyester fiber can be 0.01 to 2.0% by weight.

Description

[0001] Related applications

[0002] This application claims priority to Japanese Patent Application 2023-221579, filed on December 27, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to liquid crystal polyester fibers and their manufacturing methods. Background Technology

[0004] Liquid crystal polyester fibers are composed of polymers with rigid molecular structures. Due to the high orientation of the molecular chains, they possess high strength, high elastic modulus, and excellent heat resistance and dimensional stability. Therefore, they are expected to be used in various applications such as general industrial materials, civil / building materials, reinforcing materials, electrical / electronic component materials, and protective clothing.

[0005] For example, Patent Document 1 (Japanese Patent Application Publication No. 2006-336147) discloses a melt-anisotropic aromatic polyester fiber, which is formed by attaching 0.05% to 2% by mass of inorganic microparticles with an average particle size of 0.001 to 1 μm to the surface of a single fiber, with a single filament fineness of 0.01 to 1.5 dtex and a strength of 15 cN / dtex or more after heat treatment.

[0006] Patent document 2 (Japanese Patent Application Publication No. 2016-169464) discloses a liquid crystal polyester monofilament, which is a monofilament composed of liquid crystal polyester, having micro-unevenness on the fiber surface, the surface roughness (Ra) of the micro-unevenness on the fiber surface being 0.015 μm or more and 0.100 μm or less, and the finest diameter ratio being 8.0% or less.

[0007] Patent document 3 (Japanese Patent Application Publication No. 2013-133576) discloses a liquid crystal polyester multifilament, wherein when the total weight of the fiber is set to 100% by weight, the liquid crystal polyester multifilament is composed of liquid crystal polyester containing 0.01 to 1% by weight of metal soap.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2006-336147

[0011] Patent Document 2: Japanese Patent Application Publication No. 2016-169464

[0012] Patent Document 3: Japanese Patent Application Publication No. 2013-133576 Summary of the Invention

[0013] The problem that the invention aims to solve

[0014] However, while liquid crystal polyester fibers have high mechanical properties, they are also hydrophobic and have low liquid absorption due to their high orientation. This can lead to problems such as poor wearing comfort in clothing applications like protective clothing, and poor adhesion to the matrix resin when used as a reinforcing material in composite materials.

[0015] Patent document 1 describes how attaching inorganic microparticles to the surface of molten anisotropic aromatic polyester fibers can suppress the adhesion between monofilaments and improve the fiber separation properties of monofilaments, thus resulting in a good hand feel when making clothes. However, simply attaching inorganic microparticles to the fiber surface is not enough to improve the absorbency.

[0016] In Patent Document 2, although micro-textures were formed by cleaving the molecular chains of liquid crystal polyester on the fiber surface with phosphate compounds, no improvement in liquid absorption was achieved even when conventional oiling agents such as phosphate compounds were applied or the shape of the fiber surface was modified.

[0017] In Patent Document 3, although a specific amount of metal soap is contained inside the fiber by melting and spinning a mixture of metal soap and liquid crystal polyester, simply containing metal soap inside the fiber does not improve the properties of the fiber surface, nor does it improve the liquid absorption.

[0018] Therefore, the purpose of this invention is to solve the above-mentioned problems and provide liquid crystal polyester fibers with excellent liquid absorption and a method for manufacturing the same.

[0019] Problem Solving Methods

[0020] In order to achieve the above-mentioned objective, the inventors of this invention conducted repeated and in-depth research and found that by attaching a fatty acid metal salt with a specific number of carbon atoms to the surface of liquid crystal polyester fiber, the liquid absorption can be improved, thereby completing this invention.

[0021] That is, the present invention can be constructed in the following ways.

[0022] [Method 1]

[0023] A liquid crystal polyester fiber, wherein a fatty acid metal salt having nine or more carbon atoms (preferably 10 to 20, more preferably 10 to 18) is attached to the fiber surface.

[0024] [Method 2]

[0025] According to the liquid crystal polyester fiber of method 1, the arithmetic mean height Sa of the fiber surface, as measured according to ISO 25178, is 7.5 nm or less (preferably 0.1 to 6.0 nm, more preferably 1.0 to 5.0 nm, and even more preferably 2.0 to 5.0 nm).

[0026] [Method 3]

[0027] The liquid crystal polyester fiber according to method 1 or 2 has a strength of 20 cN / dtex or more (preferably 22 cN / dtex or more, more preferably 24 cN / dtex or more).

[0028] [Method 4]

[0029] According to any one of the methods 1 to 3, the amount of the above-mentioned fatty acid metal salt attached is 0.01 to 2.0% by weight (preferably 0.03 to 1.5% by weight, more preferably 0.1 to 1.0% by weight, even more preferably 0.1 to 0.9% by weight, and even more preferably 0.1 to 0.8% by weight).

[0030] [Method 5]

[0031] The liquid crystal polyester fiber according to any one of methods 1 to 4, wherein the amount of inorganic particles attached is 100 ppm by weight or less (preferably 10 ppm by weight or less, more preferably 1 ppm by weight or less).

[0032] [Method 6]

[0033] The liquid crystal polyester fiber according to any one of methods 1 to 5, wherein the maximum height difference PV of the fiber surface, measured according to ISO 25178, is 1 to 80 nm (preferably 10 to 60 nm, more preferably 20 to 40 nm).

[0034] [Method 7]

[0035] The liquid crystal polyester fiber according to any one of methods 1 to 6 has a liquid absorption rate of 5.0% / μm or more per unit circumference (preferably 5.0 to 20% / μm, more preferably 6.0 to 15% / μm, and even more preferably 7.0 to 10% / μm).

[0036] [Method 8]

[0037] The liquid crystal polyester fiber according to any one of the methods 1 to 7 has a metal-fiber dynamic friction coefficient of 0.18 or less (preferably 0.17 or less, more preferably 0.16 or less).

[0038] [Method 9]

[0039] A fiber structure comprising at least a portion of liquid crystal polyester fibers as described in any of embodiments 1 to 8.

[0040] [Method 10]

[0041] A method for manufacturing liquid crystal polyester fiber, the method comprising: imparting a fatty acid metal salt having 9 or more carbon atoms (preferably 10 to 20, more preferably 10 to 18) onto the surface of the liquid crystal polyester fiber.

[0042] [Method 11]

[0043] The method for manufacturing liquid crystal polyester fiber according to method 10 further comprises: a step of heat-treating the spinning precursor of the liquid crystal polyester fiber, wherein the above-mentioned heat-treating step is performed before and / or after the heat-treating step.

[0044] [Method 12]

[0045] According to the method for manufacturing liquid crystal polyester fiber of embodiment 11, the above-mentioned imparting step is performed at least before the above-mentioned heat treatment step.

[0046] When used in this specification, unless explicitly stated otherwise, the singular forms “a,” “an,” and “the” refer to the plural form containing “at least one.” When used in this specification, the terms “and / or,” “at least one,” and “more than one” include any and all combinations of the relevant listed items.

[0047] It should be noted that any combination of at least two constituent elements disclosed in the claims and / or specification is included in this invention. In particular, any combination of two or more claims recited in the claims is also included in this invention.

[0048] The effects of the invention

[0049] The liquid crystal polyester fiber of the present invention has excellent liquid absorption properties. Detailed Implementation

[0050] [Liquid Crystal Polyester Fiber]

[0051] Liquid crystal polyester fibers comprise liquid crystal polyesters. As liquid crystal polyesters, they are formed, for example, from structural units derived from aromatic diols, aromatic dicarboxylic acids, aromatic hydroxycarboxylic acids, etc. There are no particular limitations on the chemical composition of the structural units derived from aromatic diols, aromatic dicarboxylic acids, and aromatic hydroxycarboxylic acids, as long as the effects of the present invention are not impaired. Furthermore, to the extent that the effects of the present invention are not impaired, the liquid crystal polyester may also be a liquid crystal polyesteramide comprising structural units derived from aromatic diamines, aromatic hydroxylamines, or aromatic aminocarboxylic acids. For example, the examples shown in Table 1 can be cited as preferred structural units.

[0052] [Table 1]

[0053]

[0054] (Where, X in the formula is selected from the following structure)

[0055]

[0056] (Where, m = 0~2, Y = substituents selected from hydrogen, halogen atom, alkyl, aryl, aralkyl, alkoxy, aryloxy, and arylalkoxy)

[0057] In the structural units in Table 1, m is an integer from 0 to 2, and Y in the formula can be any independent hydrogen atom, halogen atom (e.g., fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), alkyl (e.g., methyl, ethyl, isopropyl, tert-butyl, etc., with 1 to 4 carbon atoms), alkoxy (e.g., methoxy, ethoxy, isopropoxy, n-butoxy, etc.), aryl (e.g., phenyl, naphthyl, etc.), aryl (e.g., benzyl (phenylmethyl), phenethyl (phenylethyl group) (phenylethyl (phenylethyl group)), aryloxy (e.g., phenoxy), arylalkoxy (e.g., benzyloxy, etc.) etc., ranging from 1 to the maximum number of substitutable atoms.

[0058] As a more preferred structural unit, the structural units described in Examples (1) to (20) shown in Tables 2, 3 and 4 below can be cited. It should be noted that when the structural unit in the formula is a structural unit that can represent multiple structures, two or more such structural units can be combined and used as structural units constituting the polymer.

[0059] [Table 2]

[0060]

[0061] [Table 3]

[0062]

[0063] [Table 4]

[0064]

[0065] In the structural units of Tables 2, 3, and 4, n is an integer of 1 or 2, and each structural unit n=1 and n=2 can exist alone or in combination. Y1 and Y2 are independent and can be hydrogen atoms, halogen atoms (e.g., fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, etc.), alkyl groups (e.g., methyl, ethyl, isopropyl, tert-butyl, etc., alkyl groups with 1 to 4 carbon atoms), alkoxy groups (e.g., methoxy, ethoxy, isopropoxy, n-butoxy, etc.), aryl groups (e.g., phenyl, naphthyl, etc.), aralkyl groups (e.g., benzyl (benzyl), phenethyl (phenylethyl), etc.), aryloxy groups (e.g., phenoxy), arylalkoxy groups (e.g., benzyloxy, etc.). Among them, hydrogen atoms, chlorine atoms, bromine atoms, or methyl groups are preferred.

[0066] In addition, Z can be represented by the substituents indicated by the following chemical formulas.

[0067] [Chemical Formula 1]

[0068]

[0069] In one embodiment, the liquid crystal polyester may contain structural units derived from hydroxycarboxylic acids as a main component. Preferably, the liquid crystal polyester may contain structural units (A) derived from hydroxybenzoic acid and structural units (B) derived from hydroxynaphthoic acid. For example, structural units (A) derived from 4-hydroxybenzoic acid (hereinafter formula (A)) can be cited as structural unit (A), and structural units (B) derived from 6-hydroxy-2-naphthoic acid (hereinafter formula (B)) can be cited as structural unit (B). From the viewpoint of improving melt-forming properties, the ratio of structural unit (A) to structural unit (B) is preferably 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.

[0070] [Chemical Formula 2]

[0071]

[0072] [Chemical Formula 3]

[0073]

[0074] The liquid crystal polyester may contain structural units derived from 4-hydroxybenzoic acid. When both structural units (A) and (B) are included, the content of the structural units derived from 4-hydroxybenzoic acid relative to the total amount of all structural units may be 50 mol% or more, preferably 53 mol% or more, more preferably 60 mol% or more, further preferably 65 mol% or more, and even more preferably 70 mol% or more. There is no particular upper limit to the content of the structural units derived from 4-hydroxybenzoic acid in the liquid crystal polyester; for example, it may be 90 mol% or less, preferably 88 mol% or less, and more preferably 85 mol% or less.

[0075] The liquid crystal polyester may contain structural units derived from 6-hydroxy-2-naphthoic acid. In the case of containing both structural units (A) and (B), the content of structural units derived from 6-hydroxy-2-naphthoic acid relative to the total amount of all structural units may be 4 to 45 mol.

[0076] Furthermore, the total content of structural unit (A) and structural unit (B) relative to the total content of all structural units can be, for example, 65 mol% or more, more preferably 70 mol% or more, and even more preferably 80 mol% or more.

[0077] In another embodiment, the liquid crystal polyester may preferably include at least one structural unit selected from the structural unit represented by formula (I) below (structural unit (I)), the structural unit represented by formula (II) below (structural unit (II)), the structural unit selected by formula (III) below (structural unit (III)), and the structural unit selected by formula (IV) below (structural unit (IV)).

[0078] -O-Ar 1 -CO-(I)

[0079] -CO-Ar 2 -CO-(II)

[0080] -O-Ar 3 -O-(III)

[0081] -O-Ar 4 -NH-(IV)

[0082] (where Ar) 1 Ar is selected from at least one of phenylene, naphthylene, and biphenylene. 2 Ar 3 and Ar 4 Each is independently selected from at least one of phenylene, naphthylene, biphenylene, and diphenyl ether dimethyl, Ar 1 Ar 2 Ar 3 and Ar 4 The hydrogen atoms of the aromatic ring may be independently replaced by halogen atoms, alkyl groups, alkoxy groups, aryl groups, aralkyl groups, aryloxy groups, or aralkoxy groups.

[0083] Structural unit (I) is a structural unit derived from aromatic hydroxycarboxylic acids, Ar 1 Preferably, it is a 1,4-phenylene structural unit (from the structural unit of 4-hydroxybenzoic acid) and a 2,6-naphthylene structural unit (from the structural unit of 6-hydroxy-2-naphthoic acid).

[0084] Structural unit (II) is a structural unit derived from an aromatic dicarboxylic acid, Ar 2 Preferably, it is a 1,4-phenylene structural unit (from the structural unit of terephthalic acid), a 1,3-phenylene structural unit (from the structural unit of isophthalic acid), a 2,6-naphthylene structural unit (from the structural unit of 2,6-naphthyldicarboxylic acid), and a diphenyl ether-4,4'-diyl structural unit (from the structural unit of diphenyl ether-4,4'-dicarboxylic acid).

[0085] Structural unit (III) is a structural unit derived from aromatic diols, Ar 3 Preferably, it is a 1,4-phenylene structural unit (from the structural unit of hydroquinone), a 4,4'-biphenylene structural unit (from the structural unit of 4,4'-dihydroxybiphenyl), a phenyl-1,4-phenylene structural unit (from the structural unit of phenylhydroquinone), and a diphenyl ether-4,4'-diyl structural unit (from the structural unit of 4,4'-dihydroxydiphenyl ether).

[0086] The structural unit (IV) is a structural unit derived from aromatic hydroxylamines, Ar 4 Preferably, it is a 1,4-phenylene structural unit (derived from the structural unit of 4-aminophenol) and a 4,4'-biphenylene structural unit (derived from the structural unit of 4-amino-4'-hydroxybiphenyl).

[0087] The content of structural unit (I) in the liquid crystal polyester can be 20-80 mol%, preferably 30-75 mol%, and more preferably 40-70 mol%, relative to the total amount of all structural units.

[0088] The content of structural unit (II) in the liquid crystal polyester can be 10-40 mol%, preferably 12.5-35 mol%, and more preferably 15-30 mol%, relative to the total amount of all structural units.

[0089] The total content of structural units (III) and (IV) in the liquid crystal polyester can be 10-40 mol%, preferably 12.5-35 mol%, more preferably 15-30 mol%, relative to the total amount of all structural units.

[0090] The molar ratio of the content of structural unit (II) to the total content of structural units (III) and (IV) in terms of (II) / [(III)+(IV)] can be 90 / 100~100 / 90, preferably 95 / 100~100 / 95, more preferably 98 / 100~100 / 98, and even more preferably 100 / 100.

[0091] In liquid crystal polyester, each structural unit (I) to (IV) may contain two or more types. The above-mentioned content of each structural unit represents the content of all structural units that conform to each structural unit. For example, when the liquid crystal polyester contains two or more structural units (I), the content of structural unit (I) represents their total content.

[0092] In the liquid crystal polyester, the total content of structural units (I) to (IV) relative to the total amount of all structural units can be, for example, 90 mol% or more, preferably 95 mol% or more, more preferably 99 mol% or more, and even more preferably 100 mol%.

[0093] The liquid crystal polyester is preferably a combination having a naphthalene skeleton as a structural unit. For example, relative to the total amount of all structural units, the total content of the 2,6-naphthylene-containing structural units in the liquid crystal polyester can be 28 mol% or more, preferably 30 mol% or more, more preferably 40 mol% or more, further preferably 50 mol% or more, even more preferably 55 mol% or more, particularly preferably 60 mol% or more, particularly more preferably 65 mol% or more, and particularly more preferably 70 mol% or more. In addition, from the viewpoint of improving melt-forming properties, the total content of the 2,6-naphthylene-containing structural units in the liquid crystal polyester relative to the total amount of all structural units can be 95 mol% or less, preferably 90 mol% or less, and more preferably 85 mol% or less. As the 2,6-naphthylene-containing structural unit, the structural unit derived from 6-hydroxy-2-naphthoic acid (structural unit (B) of the above formula (B)) and Ar are preferred. 1 The structural unit is 2,6-naphthylene (I) and the structural unit is derived from 2,6-naphthoic acid (Ar). 2 It is a 2,6-naphthyl structural unit (II)).

[0094] The melting point (hereinafter sometimes referred to as Mp0) of the liquid crystal polyester is preferably in the range of 250~380°C, more preferably 255~370°C, even more preferably 260~360°C, even more preferably 260~340°C, and particularly preferably 260~330°C. In this specification, the melting point is the temperature of the main absorption peak observed by differential scanning calorimetry (DSC) according to the JIS K 7121 test method. Specifically, in the DSC apparatus, 4~6 mg of sample is sealed in an aluminum dish, and nitrogen gas, as the carrier gas, is circulated at a flow rate of 200 mL / min. The endothermic peak is measured when the temperature is increased from room temperature (e.g., 25°C) at a rate of 10°C / min. Depending on the type of polymer, in DSC determination, if no clear peak appears in the first run, the temperature is increased to 50°C higher than the expected flow temperature at 50°C / min. After complete melting at this temperature for 3 minutes, the temperature is cooled to 50°C at a rate of 80°C / min, and then the endothermic peak is measured at a rate of 10°C / min.

[0095] It should be noted that, without impairing the effects of the present invention, thermoplastic polymers such as polyethylene terephthalate, modified polyethylene terephthalate, polyolefins, polycarbonate, polyamide, polyphenylene sulfide, polyetheretherketone, and fluoropolymers can be mixed into the liquid crystal polyester. Additionally, various additives such as titanium dioxide, kaolin, silicon dioxide, barium oxide, carbon black, dyes or pigments, antioxidants, ultraviolet absorbers, and light stabilizers can also be mixed in.

[0096] Provided that the effects of the present invention are not impaired, the liquid crystal polyester fiber can be a mixed spun fiber obtained by spinning a mixture of liquid crystal polyester with the aforementioned thermoplastic polymer and various additives, or it can be a composite spun fiber obtained by simultaneously spinning from a spinning spinneret that distinguishes different components of the liquid crystal polyester and the aforementioned thermoplastic polymer. The liquid crystal polyester fiber can be a non-composite spun fiber or a composite spun fiber. It is particularly preferred that the liquid crystal polyester is present on the fiber surface, and it is more preferable that the fatty acid metal salt described later is attached to the fiber surface composed of the liquid crystal polyester.

[0097] The liquid crystal polyester fiber may contain more than 50% by weight of liquid crystal polyester, preferably more than 80% by weight, more preferably more than 90% by weight, further preferably more than 95% by weight, and even more preferably more than 98% by weight.

[0098] Liquid crystal polyester fibers have fatty acid metal salts with nine or more carbon atoms attached to their surface. In this case, the liquid crystal polyester fiber consists of a fiber body and a surface attachment portion. The fiber body is primarily composed of liquid crystal polyester, and the surface attachment portion is formed to cover the fiber body and contains fatty acid metal salts with nine or more carbon atoms. This invention has found that by attaching fatty acid metal salts with a specific number of carbon atoms to the surface of the liquid crystal polyester fiber, liquid absorbency is improved. It can be inferred that when an amphiphilic oil is attached to the surface of the liquid crystal polyester fiber, the hydrophobic portion of the oil faces the hydrophobic surface of the liquid crystal polyester fiber, and the hydrophilic portion faces outward, thus increasing hydrophilicity and liquid absorbency. In the case of amphiphilic oils such as phosphate oils (excluding carboxylic acid metal salts) and fatty acid metal salts with short carbon chains, the effect of improving liquid absorbency cannot be fully exerted. In contrast, it has been found that with fatty acid metal salts having a specific number of carbon atoms, the long carbon chain and carboxyl groups may interact with the liquid crystal polyester molecules, thereby improving liquid absorbency.

[0099] The fatty acids in a fatty acid metal salt having nine or more carbon atoms can be any type of saturated or unsaturated fatty acid, or hydroxy fatty acids containing a hydroxyl group. Examples include nonanoic acid, decanoic acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, nonadecanoic acid, arachidic acid, dodecanoic acid, behenic acid, limonic acid, ceric acid, linoleic acid, beeswax acid, myristoleic acid, myristolenic acid, palmitoleic acid, oleic acid, transoleic acid, linoleic acid, linolenic acid, gadolinic acid, eicosapentaenoic acid, arachidonic acid, erucic acid, hydroxystearic acid, and ricinoleic acid. These fatty acids can be contained individually or in combination with two or more. From the viewpoint of improving the absorbency of liquid crystal polyester fibers and having good solubility or dispersibility in water so as to facilitate application as an oiling agent, the number of carbon atoms in the fatty acids is preferably 10 to 20, more preferably 10 to 18.

[0100] Examples of fatty acid metal salts having 9 or more carbon atoms include lithium, sodium, potassium, magnesium, calcium, barium, aluminum, and zinc salts. Among these, alkali metal salts such as lithium, sodium, and potassium are preferred. Potassium salts are more preferred from the viewpoint of high water solubility and ease of application as an oiling agent. Examples of fatty acid metal salts having 9 or more carbon atoms include potassium decanoate, potassium laurate, potassium myristate, potassium palmitate, potassium stearate, potassium oleate, and potassium linoleate. In liquid crystal polyester fibers, as long as a fatty acid metal salt having 9 or more carbon atoms is attached to the fiber surface, components other than fatty acid metal salts having 9 or more carbon atoms (e.g., amphiphilic compounds other than fatty acid metal salts, fatty acid metal salts having 8 or fewer carbon atoms) can be included to the extent that the effects of the present invention are not compromised.

[0101] From the viewpoint of improving liquid absorption, the amount of the aforementioned fatty acid metal salt adhering to the liquid crystal polyester fiber can be 0.01% by weight or more, preferably 0.03% by weight or more, and more preferably 0.1% by weight or more. The amount of the aforementioned fatty acid metal salt adhering can be 2.0% by weight or less, preferably 1.5% by weight or less. Furthermore, from the viewpoint of reducing the arithmetic mean height Sa of the fiber surface, it is more preferably 1.0% by weight or less, further preferably 0.9% by weight or less, and even more preferably 0.8% by weight or less. In this specification, the amount of the aforementioned fatty acid metal salt adhering represents the ratio of the amount of the aforementioned fatty acid metal salt adhering to the total weight of the fiber including the adhering material on the fiber surface, and is a value measured by the method described in the examples described later.

[0102] The liquid absorption rate per unit circumference of the liquid crystal polyester fiber can be 5.0% / μm or more, preferably 6.0% / μm or more, and more preferably 7.0% / μm or more. Furthermore, there is no particular upper limit to the liquid absorption rate per unit circumference; for example, it can be 20% / μm or less. In applications where controlled liquid absorption is required, it is preferably 15% / μm or less, and more preferably 10% / μm or less. In this specification, the liquid absorption rate per unit circumference represents the liquid absorption rate (water absorption rate) based on the circumference of the cross-section of a single fiber calculated according to the fiber fineness, with the fiber cross-section considered as a perfect circle. It can be measured by the method described in the examples below.

[0103] The arithmetic mean height Sa of the surface of the liquid crystal polyester fiber can be 7.5 nm or less. The arithmetic mean height Sa of the fiber surface is affected by the state of the surface attachment portion. When a fatty acid metal salt with a specific number of carbon atoms is attached, the long carbon chain and carboxyl groups of the fatty acid metal salt interact with the liquid crystal polyester molecules on the fiber surface, causing the fatty acid metal salt to move and homogenize by covering the fiber surface, thus reducing the unevenness of the fiber surface. This is achievable when using a fatty acid metal salt with a specific number of carbon atoms. When using a fatty acid metal salt with 8 or fewer carbon atoms, the interaction with the liquid crystal polyester molecules may not be fully utilized, thus potentially failing to sufficiently reduce the arithmetic mean height Sa of the fiber surface. By controlling the arithmetic mean height Sa of the fiber surface within a specific range, the coefficient of friction with the friction object can be reduced, resulting in excellent wear resistance. The arithmetic mean height Sa of the fiber surface is preferably 6.0 nm or less, more preferably 5.0 nm or less, and can be 0.1 nm or more, preferably 1.0 nm or more, and more preferably 2.0 nm or more. The arithmetic mean height Sa represents the average of the absolute values ​​of the differences between the heights of points in a defined area and the average surface area, as determined according to ISO 25178. In this specification, the arithmetic mean height Sa is determined by the method described in the examples below.

[0104] The arithmetic mean roughness Ra of the surface of the liquid crystal polyester fiber can be 20 nm or less. Preferably, the arithmetic mean roughness Ra of the fiber surface is 14 nm or less, more preferably 12 nm or less, and even more preferably 10 nm or less. It can also be 0.1 nm or more, preferably 1.0 nm or more, and even more preferably 3.0 nm or more. Furthermore, the arithmetic mean roughness Ra of the fiber surface can be 0.1 to 20 nm, preferably 0.1 to 14 nm, more preferably 1.0 to 12 nm, and even more preferably 3.0 to 10 nm. The arithmetic mean roughness Ra refers to an index of the roughness in the height direction measured according to JIS B 0601:2001. In a roughness curve along a reference length, it represents the unevenness of the interval as the average of the absolute values ​​of the deviations from the mean line to the roughness curve. In this specification, the arithmetic mean roughness Ra is measured based on the profile curve of the surface along the fiber axis of a single fiber, and is measured by the method described in the examples below.

[0105] The maximum height difference (PV) on the surface of the liquid crystal polyester fiber can be 80 nm or less, preferably 60 nm or less, more preferably 40 nm or less, and can also be 1 nm or more, preferably 10 nm or more, and more preferably 20 nm or more. Furthermore, the maximum height difference (PV) on the fiber surface can be 1 to 80 nm, preferably 10 to 60 nm, and more preferably 20 to 40 nm. The maximum height difference (PV) refers to the sum of the maximum peak height and the maximum valley depth of the profile curve in the reference length measured according to ISO 25178. In this specification, the maximum height difference (PV) is measured by the method described in the examples described later.

[0106] From the viewpoint of adjusting surface roughness to achieve low friction, the amount of inorganic particles attached to the liquid crystal polyester fiber can be 100 ppm by weight or less, preferably 10 ppm by weight or less, and more preferably 1 ppm by weight or less. In this specification, the amount of inorganic particles attached refers to the ratio of the amount of inorganic particles attached to the total weight of the fiber, including the attachment on the fiber surface.

[0107] The metal-fiber dynamic friction coefficient of the liquid crystal polyester fiber can be 0.18 or less, preferably 0.17 or less, and more preferably 0.16 or less. Furthermore, the lower limit of the metal-fiber dynamic friction coefficient is not particularly limited, and for example, it can be 0.10 or more. In this specification, the metal-fiber dynamic friction coefficient is measured by the method described in the examples below.

[0108] The strength of the liquid crystal polyester fiber can be 20 cN / dtex or higher, preferably 22 cN / dtex or higher, and more preferably 24 cN / dtex or higher. Furthermore, the upper limit of the tensile strength is not particularly limited, and for example, it can be around 40 cN / dtex. In this specification, the strength of the liquid crystal polyester fiber refers to the tensile strength, which is a value measured by the method described in the examples below.

[0109] The single fiber fineness of the liquid crystal polyester fiber can be appropriately selected according to the application, etc. For example, the single fiber fineness can be 50 dtex or less, preferably 15 dtex or less, and more preferably 10 dtex or less. Furthermore, there is no particular limitation on the lower limit of the single fiber fineness; for example, it can be around 0.01 dtex. The single fiber fineness is a value measured by the method described in the examples below.

[0110] Liquid crystal polyester fibers can be monofilaments or multifilaments. In the case of multifilaments, the number of filaments can be appropriately selected according to the application, for example, the number of filaments can be 2 to 5,000, preferably 3 to 4,000, and more preferably 5 to 3,000.

[0111] The total fineness of the liquid crystal polyester fiber can be appropriately selected according to its application, etc. For example, the total fineness can be less than 50,000 dtex, preferably less than 10,000 dtex, more preferably less than 5,000 dtex, and even more preferably less than 2,000 dtex. In addition, there is no particular limitation on the lower limit of the total fineness, for example, it can be around 1 dtex.

[0112] [Manufacturing method of liquid crystal polyester fiber]

[0113] A method for manufacturing liquid crystal polyester fibers includes a step of imparting a fatty acid metal salt having nine or more carbon atoms to the surface of the liquid crystal polyester fiber. This invention has found that by attaching a fatty acid metal salt having a specific number of carbon atoms to the surface of the liquid crystal polyester fiber, liquid absorbency is improved.

[0114] In the process of imparting fatty acid metal salts, the aforementioned fatty acid metal salts can be used as the form in which they are imparted to the liquid crystal polyester fibers. These salts can be either an oil solution in which the fatty acid metal salt is dissolved in a medium, or an oil dispersion in which the fatty acid metal salt is dispersed in a medium. The imparting method is not particularly limited; known imparting methods such as impregnation, spraying, coating, and immersion-rolling are examples. It is preferable to use an oiling guide such as an oiling roller or a beak-type oiler to impart the salt to the traveling liquid crystal polyester fibers.

[0115] In the manufacturing method of liquid crystal polyester fiber, a further step can be taken to heat-treat the spinning precursor of the liquid crystal polyester fiber. By heat-treating the spinning precursor of the liquid crystal polyester fiber to carry out solid-state polymerization of the liquid crystal polyester, the strength of the fiber can be improved.

[0116] In cases where a heat treatment process is included, the application of fatty acid metal salts can be performed before and / or after the heat treatment process. Before the heat treatment process, the fatty acid metal salt can be applied to the spinning precursor of the liquid crystal polyester fiber, for example, during the winding of the spun precursor, or during the unwinding of the temporarily wound spun precursor. After the heat treatment process, the fatty acid metal salt can be applied to the heat-treated liquid crystal polyester fiber, for example, as a finishing oil.

[0117] From the viewpoint of improving liquid absorbency, the application of fatty acid metal salts is preferably performed at least before the heat treatment process. The mechanism of action is not yet certain, but when a fatty acid metal salt with a specific number of carbon atoms is applied to the spinning precursor followed by heat treatment, it is possible that the fatty acid metal salt, applied in the form of an aqueous solution or the like, becomes oven-dry and thus readily absorbs moisture, thereby improving liquid absorbency.

[0118] In the process of applying fatty acid metal salts, from the viewpoint of improving the liquid absorption of liquid crystal polyester fibers, the application of the fatty acid metal salt can be carried out at an amount of 0.01% by weight or more, preferably at 0.03% by weight or more, and more preferably at 0.1% by weight or more. Furthermore, if the fatty acid metal salt application process is performed before the heat treatment process, excessive amounts of fatty acid metal salt on the liquid crystal polyester fibers supplied for heat treatment may hinder the solid-state polymerization during heat treatment, thus potentially resulting in insufficient strength improvement. Therefore, from the viewpoint of not hindering the solid-state polymerization during heat treatment, the application of the fatty acid metal salt can be carried out at an amount of 2.0% by weight or less, preferably at 1.5% by weight or less, more preferably at 1.0% by weight or less, further preferably at 0.9% by weight or less, and even more preferably at 0.8% by weight or less. By applying a fatty acid metal salt with a specific number of carbon atoms to the fatty acid metal salt at such an amount, the strength can be sufficiently improved in the subsequent heat treatment, thus achieving a balance between liquid absorption and strength. On the other hand, in the case of fatty acid metal salts with 8 or fewer carbon atoms, the solid-state polymerization of liquid crystal polyester may be hindered because the balance of amphiphilicity may affect the morphology imparted to the fiber surface, thus there is a tendency that the strength cannot be adequately improved by heat treatment.

[0119] The heat treatment method is not particularly limited; for example, it can be batch heat treatment or continuous heat treatment via conveying. In batch heat treatment, for example, heat treatment can be performed by winding the material onto a bobbin in a roll, strand, or tow; considering the simplification of equipment and improvement of productivity, rolling is preferred. In the case of continuous heat treatment via conveying, the conveying method can be any of contact conveying (e.g., conveyor belt method, support roller method, heated roller heat treatment method) or non-contact conveying (roll-to-roll method).

[0120] Heat treatment can be performed using known methods, such as heating in a gas atmosphere or contact heating. Suitable gas atmospheres include air, inert gases (e.g., nitrogen, argon), or combinations thereof. Furthermore, heat treatment can be performed even under reduced pressure without any problems.

[0121] The heat treatment temperature can be 230°C or higher, and from the viewpoint of efficiently improving strength, 240°C or higher is preferred, and 250°C or higher is more preferable. Furthermore, to prevent melting, the heat treatment temperature can be lower than the melting point (Mp) of the spinning precursor fiber supplied to the heat treatment process. For example, within the range of 230°C or higher, it can be Mp-50°C or higher and lower than Mp°C, preferably Mp-40°C or higher and lower than Mp°C, and more preferably Mp-30°C or higher and lower than Mp°C. In the heat treatment process, since the melting point of the liquid crystal polyester fiber increases as solid-state polymerization proceeds, it is sufficient to set the initial heat treatment temperature in the heat treatment process to be lower than the melting point (Mp) of the spinning precursor fiber. From the viewpoint of efficiently improving strength, the heat treatment temperature can be gradually increased according to the progress of solid-state polymerization, and heat treatment can be performed at a temperature exceeding the melting point (melting point of the spinning precursor fiber) at the time of supply to the heat treatment process.

[0122] The heat treatment time can be appropriately set according to the heat treatment method and the heat treatment temperature. For example, it can be set from 15 minutes to 30 hours, preferably 2 to 24 hours, and more preferably 3 to 20 hours, where the heat treatment time refers to the holding time at a given heat treatment temperature.

[0123] In the manufacturing method of liquid crystal polyester fiber, the strength ratio of the liquid crystal polyester fiber before and after the heat treatment process can be 1.5 times or more, preferably 1.8 times or more, and more preferably 2.0 times or more. There is no particular upper limit to the strength ratio of the liquid crystal polyester fiber before and after the heat treatment process; for example, it can be 10 times or less. Here, the strength ratio before and after the heat treatment process refers to the value obtained by dividing the strength of the liquid crystal polyester fiber after the heat treatment process by the strength of the liquid crystal polyester fiber (spinning precursor) before the heat treatment process.

[0124] [Fiber Structure]

[0125] Liquid crystal polyester fibers can be used for various applications as fiber structures containing at least a portion thereof. Fiber structures containing liquid crystal polyester fibers can be used in any fiber form, such as staple fibers, chopped strands, filament yarns, spun yarns, ropes, cords, etc. Furthermore, they can be used as various fabrics, such as nonwoven fabrics, woven fabrics, and knitted fabrics, that utilize liquid crystal polyester fibers. Such fibers and fabrics can be manufactured using known methods using liquid crystal polyester fibers.

[0126] Provided that the effects of the present invention are not compromised, the fiber structure can be made by combining liquid crystal polyester fibers with other fibers. For example, composite fibers using liquid crystal polyester fibers and other fibers can be used (e.g., blended filaments made by mixing liquid crystal polyester fibers and other fibers). In addition, composite fabrics using liquid crystal polyester fibers and other fibers can be used (e.g., blended fabrics made by mixing liquid crystal polyester fibers and other fibers, laminates of fabrics formed from liquid crystal polyester fibers and fabrics formed from other fibers, etc.).

[0127] Liquid crystal polyester fiber can be used in various fiber structures for a wide range of applications, including general industrial materials, civil / building materials, various reinforcing materials, electrical / electronic component materials, and various fiber products. Examples include tensile components (wires, optical fibers, umbilical cables, heating wires, headphone wires, and other electrical product wires), canvas, ropes (marine, mountaineering, crane, sailboat, tugboat, etc.), climbing ropes, sports nets (safety nets, golf driving range nets, etc.), slings, lifelines, fishing lines, sewing threads, window screen ropes, fishing nets, rope hooks, geogrids, protective gloves, tear-resistant materials for protective clothing / outdoor garments, cycling apparel, sports rackets, racket strings, reinforcing materials for medical catheters, sutures, mesh fabrics, filters, base fabrics for printed circuit boards, outer materials for electronic devices, mesh conveyor belts, papermaking belts, dryer canvas, airships, balloons, airbags, speaker cones, reinforcing materials for various hoses / pipes, and reinforcing materials for rubber / plastics such as tires / conveyor belts, among other high-end processed products.

[0128] Example

[0129] The present invention will now be described in more detail based on embodiments, but the invention is not limited thereto. It should be noted that in the following embodiments and comparative examples, various physical properties were measured using the methods described below.

[0130] (Melting point of resin chips (granular molded parts))

[0131] According to JIS K 7121, a differential scanning calorimeter (DSC; Shimadzu Corporation "DSC60APlus") was used for measurement, and the observed main absorption peak temperature was taken as the melting point. Specifically, in the above-mentioned DSC apparatus, 4-6 mg of sample was sealed in an aluminum dish, and nitrogen gas, used as the carrier gas, was circulated at a flow rate of 200 mL / min. The endothermic peak from the liquid crystal polyester was measured when the temperature was increased from 25°C to 10°C / min.

[0132] (Total fineness, single fiber fineness)

[0133] Based on JIS L 1013:2010 8.3.1 A method, a 10m length of liquid crystal polyester fiber was twisted using a "Wrap Reel by Motor Driven" measuring instrument manufactured by Daiei Scientific Precision Machinery Co., Ltd. The weight (g) was multiplied by 1000, and measurements were performed three times at each level. The average of the three measurements was taken as the total fineness (dtex) of the obtained liquid crystal polyester fiber. Furthermore, the quotient obtained by dividing this value by the number of fibers was taken as the fineness (dtex) of a single fiber.

[0134] (Arithmetic mean height Sa and maximum elevation difference PV)

[0135] A single fiber was taken from a liquid crystal polyester fiber (multifilament), and the fiber surface was measured under the following conditions using a scanning probe microscope (Hitachi High-Tech "Environmentally Controlled Unit E-sweep").

[0136] Measurement mode: DFM mode

[0137] Cantilever: SI-DF20 (Silicon)

[0138] Scan range: 2μm × 2μm

[0139] Pixel count: 256×256 pixels

[0140] Measurement environment: 23℃, 40%RH, atmospheric conditions

[0141] After performing three tilt corrections on the obtained image data, the arithmetic mean height Sa and the maximum height difference PV were calculated based on the corrected images. Measurements were performed on five single fibers, and the average values ​​of their respective arithmetic mean height Sa and maximum height difference PV were determined.

[0142] (Arithmetic mean roughness Ra)

[0143] A single fiber was taken from a liquid crystal polyester fiber (multifilament), and the fiber surface was measured under the following conditions using a scanning probe microscope (Hitachi High-Tech "Environmentally Controlled Unit E-sweep").

[0144] Measurement mode: DFM mode

[0145] Cantilever: SI-DF20 (Silicon)

[0146] Scan range: 10μm × 10μm

[0147] Pixel count: 256×256 pixels

[0148] Measurement environment: 23℃, 40%RH, atmospheric conditions

[0149] After performing three tilt corrections on the obtained image data, a line was drawn parallel to the fiber's length direction at the center of the fiber, and the arithmetic mean roughness Ra was calculated. Measurements were performed on five individual fibers, and the average arithmetic mean roughness Ra for each fiber was determined.

[0150] (Amount of fatty acid metal salts attached)

[0151] 10 g of liquid crystal polyester fiber sample and 1 mg of internal standard were extracted with 100 mL of methanol for 24 hours, and the methanol phase was concentrated using an evaporator. The residue was measured using a gas chromatograph (Shimadzu Corporation GC-8A and CR-6A Chromatopack) at an injection temperature of 340 °C, FID detector, detector temperature of 340 °C, and a heating rate of 15 °C / min from 60 °C to 340 °C. The peak area ratio of the internal standard to the fatty acid metal salt was calculated. The content of the fatty acid metal salt was calculated as peak area of ​​fatty acid metal salt / peak area of ​​internal standard × content of internal standard (1 mg). The fatty acid metal salt content relative to 10 g of liquid crystal polyester fiber sample was determined as the amount of fatty acid metal salt attached (weight %).

[0152] (Amount of inorganic particles attached)

[0153] The amount of inorganic particles adhering to the liquid crystal polyester fiber was determined by Soxhlet extraction. Specifically, 5g of liquid crystal polyester fiber coated with an oil containing fatty acid metal salts and inorganic particles was placed in a Soxhlet extractor. Methanol and zeolite were added to a flat-bottomed flask, and extraction was carried out in a 10L water bath (100℃) for 1.5 hours. Then, the methanol was evaporated, and the weight of the extracted oil was measured. The oil adhesion rate was calculated gravimetrically based on the weight of the liquid crystal polyester fiber before extraction. The amount of inorganic particles adhering to the fiber was calculated based on the obtained oil adhesion rate and the ratio of fatty acid metal salts to inorganic particles in the oil.

[0154] (strength)

[0155] Referring to JIS L 1013:2010 8.5.1, using the USTER Technologies "TENSORAPID5" tensile elongation tester, each sample was subjected to 5 tensile tests under the conditions of a test length of 30 cm, a tensile speed of 15 cm / min, and an initial load of 0.33 g / dtex. The tensile strength (cN / dtex) was calculated by dividing the average tensile strength (cN) of the 5 tests by the total fineness (dtex) measured by the above method.

[0156] (Liquid absorption rate per unit circumference)

[0157] Ten single fibers were separated from liquid crystal polyester fiber (multifilament), and 20 cm lengths of each fiber were collected and recycled to a pre-weighed vinyl sheet. The total weight A of the ten single fibers was measured. Each single fiber was then immersed in water and allowed to stand for 1 minute, and the total weight B of the ten single fibers was measured again. Based on these measurements, the liquid absorption rate (%) of each single fiber was calculated using the following formula. This measurement was performed three times, and the average value C was calculated.

[0158] Liquid absorption rate per single fiber (%) = (BA) / (A × 10) × 100

[0159] Assuming the fiber cross-section is a perfect circle, the circumference D (μm) of the single fiber cross-section is calculated based on the single fiber fineness (dtex) measured by the above method, and the liquid absorption rate per unit circumference is calculated by the following formula.

[0160] Liquid absorption rate per unit circumference (% / μm) = C / D

[0161] (Coefficient of kinetic friction between metal and fiber)

[0162] The dynamic friction coefficient between metal and fiber was determined using a Röder method fiber friction coefficient measuring machine (manufactured by Kui Seiki Research Institute) with liquid crystal polyester fiber and a friction element test piece (Φ8mm chrome-plated rough surface) in a gas atmosphere of 25°C and 40%RH under conditions of a load of 500g and a speed of 0.1cm / min. Measurements were performed on two fibers, and the average value was taken as the dynamic friction coefficient between metal and fiber.

[0163] [Example 1]

[0164] Chips (Mp0: 278°C) of liquid crystal polyester (Mp0: 278°C), composed of structural units from 4-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid in a 73 / 27 (mol%) ratio, were hot-air dried at 120°C for more than 4 hours. Then, melt extrusion was performed using a single-screw extruder, with the melt compound being metered and fed to the spinneret using a gear pump. In the spinneret, the melt compound was filtered using a metal nonwoven filter, and extruded from a 40-hole spinneret with a 0.10 mm Φ orifice and a land length of 0.14 mm at a rate of 17.6 g / min. For the ejected filaments, an aqueous solution of potassium decanoate at a concentration of 1.6% by weight is applied as a spinning oil through an oiling guide located directly below the spinning spinneret. The oil is then drawn to the first guide roller, and after passing through the second guide roller, it is wound into a bobbin shape by a winding machine at a speed of 800 m / min via a tension regulating roller, resulting in a spinning precursor of 220 dtex / 40 filaments.

[0165] The obtained spun yarn was unwound longitudinally (perpendicular to the fiber winding direction) using a rewinding machine and then unwound onto a bobbin made of nonwoven fabric wound on a perforated stainless steel bobbin, resulting in a heat-treated bobbin package. The package was then heat-treated at 275°C for 16 hours in a nitrogen atmosphere to obtain heat-treated liquid crystal polyester fiber. Next, the heat-treated fiber was unwound transversely (horizontally relative to the fiber winding direction) using a rewinding machine, during which a finishing oil agent primarily composed of coconut oil was applied. The analytical results of the obtained liquid crystal polyester fiber are shown in Table 5.

[0166] [Example 2]

[0167] Except that the potassium decanoate aqueous solution was given an increased amount of potassium decanoate, liquid crystal polyester fibers were obtained in the same manner as in Example 1.

[0168] [Example 3]

[0169] Except that potassium stearate aqueous solution was used as a spinning oil, liquid crystal polyester fibers were obtained in the same manner as in Example 1.

[0170] [Example 4]

[0171] Except for obtaining a spinning precursor of 56 dtex / 10 filaments by spraying the molten compound at a rate of 4.48 g / min using a spinning spinneret with an aperture of 0.10 mmΦ, a path length of 0.14 mm, and 10 holes, liquid crystal polyester fibers were obtained in the same manner as in Example 1.

[0172] [Example 5]

[0173] In addition to obtaining a spinning precursor of 1670 dtex / 300 filaments by spraying the molten compound at a rate of 64.0 g / min using a spinning spinneret with an aperture of 0.10 mmΦ, a path length of 0.14 mm, and 300 holes, liquid crystal polyester fibers were obtained in the same manner as in Example 1.

[0174] [Example 6]

[0175] Except that the potassium decanoate aqueous solution was given an increased amount of potassium decanoate, liquid crystal polyester fibers were obtained in the same manner as in Example 1.

[0176] [Example 7]

[0177] Except for the use of a spinning oil containing 1.6% by weight of potassium decanoate and 0.13% by weight of mica, liquid crystal polyester fibers were obtained in the same manner as in Example 1. The amount of mica attached to the obtained liquid crystal polyester fibers was 0.11% by weight.

[0178] [Example 8]

[0179] Except for obtaining a spinning precursor of 1670 dtex / 600 filaments by spraying the molten compound at a rate of 64.0 g / min using a spinning spinneret with an aperture of 0.08 mmΦ, a path length of 0.112 mm, and 600 holes, liquid crystal polyester fibers were obtained in the same manner as in Example 1.

[0180] [Example 9]

[0181] Except that sodium dodecyl phosphate aqueous solution was used as the spinning oil and potassium decanoate aqueous solution was used as the finishing oil, liquid crystal polyester fibers were obtained in the same manner as in Example 1.

[0182] [Comparative Example 1]

[0183] Except that potassium octanoate aqueous solution was used as the spinning oil, liquid crystal polyester fibers were obtained in the same manner as in Example 1.

[0184] [Comparative Example 2]

[0185] Except that an aqueous solution of sodium dodecyl phosphate was used as the spinning oil, liquid crystal polyester fibers were obtained in the same manner as in Example 1. It should be noted that the amount of sodium dodecyl phosphate applied was 0.62% by weight.

[0186]

[0187] As shown in Table 5, in Examples 1 to 9, since the fatty acid metal salt with a specific number of carbon atoms used as an oiling agent is attached to the liquid crystal polyester fiber, the liquid absorption rate per unit circumference is high and the liquid absorption is excellent.

[0188] Furthermore, in Examples 1-6, 8, and 9, since a fatty acid metal salt with a specific number of carbon atoms was used as the adhering oil and no inorganic particles were adhering, the arithmetic mean height Sa could be adjusted to be low. Similarly, the arithmetic mean roughness Ra and the maximum height difference PV could also be adjusted to be low. Therefore, the coefficient of dynamic friction between the metal and fiber is low, resulting in excellent wear resistance.

[0189] In Examples 1-5, 7 and 8, the strength was adequately improved in the subsequent heat treatment because the amount of fatty acid metal salts used as spinning oil was adjusted.

[0190] On the other hand, in Comparative Example 1, which used a fatty acid metal salt with a small number of carbon atoms, the liquid absorption rate per unit circumference was low and the liquid absorption was poor compared to Examples 1-9. Furthermore, in Comparative Example 1, compared to Examples 1 and 3 with different numbers of carbon atoms in the fatty acid metal salt, the arithmetic mean height Sa was larger, resulting in a higher coefficient of dynamic friction between the metal and fiber and poor wear resistance. Moreover, in Comparative Example 1, compared to Examples 1 and 3 with the same or higher amount of fatty acid metal salt adhesion, the strength was significantly reduced, and it did not possess sufficient strength.

[0191] In addition, in Comparative Example 2, which used sodium dodecyl phosphate as an oiling agent, the liquid absorption rate per unit circumference was low and the liquid absorption was poor compared with Examples 1-9.

[0192] Industrial applicability

[0193] Liquid crystal polyester fibers can be used in a variety of applications, including general industrial materials, civil / building materials, various reinforcing materials, electrical / electronic component materials, and various fiber products.

[0194] As described above, preferred embodiments of the present invention have been explained. However, various additions, modifications, or deletions may be made without departing from the spirit of the present invention, and all of these are included within the scope of the present invention.

Claims

1. A liquid crystal polyester fiber, wherein a fatty acid metal salt having nine or more carbon atoms is attached to the fiber surface.

2. The liquid crystal polyester fiber according to claim 1, wherein, The arithmetic mean height Sa of the fiber surface, as determined according to ISO 25178, is less than 7.5 nm.

3. The liquid crystal polyester fiber according to claim 1 or 2, wherein the strength is 20 cN / dtex or higher.

4. The liquid crystal polyester fiber according to claim 1 or 2, wherein, The amount of the fatty acid metal salt attached is 0.01~2.0 by weight.

5. The liquid crystal polyester fiber according to claim 1 or 2, wherein, The amount of inorganic particles attached is less than 100 ppm by weight.

6. The liquid crystal polyester fiber according to claim 1 or 2, wherein, The maximum surface elevation difference (PV) of the fiber, as determined according to ISO 25178, is 1~80 nm.

7. The liquid crystal polyester fiber according to claim 1 or 2, wherein the liquid absorption rate per unit circumference is 5.0% / μm or higher.

8. The liquid crystal polyester fiber according to claim 1 or 2, wherein the coefficient of dynamic friction between the metal and the fiber is less than 0.

18.

9. A fiber structure comprising at least a portion of the liquid crystal polyester fiber as described in claim 1 or 2.

10. A method for manufacturing liquid crystal polyester fiber, the method comprising: The process of imparting a fatty acid metal salt with nine or more carbon atoms to the surface of a liquid crystal polyester fiber.

11. The manufacturing method according to claim 10, further comprising: The process of heat-treating the spinning precursor of liquid crystal polyester fiber, wherein the imparting process is performed before and / or after the heat treatment process.

12. The manufacturing method according to claim 11, wherein, The imparting process is performed at least before the heat treatment process.

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