Liquid crystal polymer fiber and method for producing the same

Abstract

To provide a liquid crystal polymer fiber having excellent wear resistance and a method for producing the same.SOLUTION: The liquid crystal polymer fiber has an arithmetic average roughness Ra of the fiber surface of 0.20 to 0.50 μm. The production method may be provided with a step of preparing a dispersion having a viscosity of 6 mPa s or more by stirring an aqueous oil solution containing a layered silicate mineral having an interlayer distance of 1.0 nm or more with a stirrer at a circumferential speed of 6 m / s or more, and a step of applying the dispersion to the liquid crystal polymer fiber so that the adhesion amount of the layered silicate mineral per unit surface area is 0.20 to 1.20 μg / cm2.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to liquid crystal polymer fibers and a method for producing the same. [Background technology]

[0002] Liquid crystal polymer fibers such as melt-dispersed aromatic polyester fibers and aramid fibers are composed of polymers with rigid molecular structures, and due to the highly oriented molecular chains, they have high strength, high elasticity, and excellent heat resistance and dimensional stability. Therefore, they are used for various purposes such as general industrial materials, civil engineering and construction materials, various reinforcing materials, electrical and electronic parts materials, and various textile products.

[0003] However, while the molecular chains of liquid crystal polymer fibers are highly oriented in the fiber axis direction, the interaction between the molecular chains in the direction perpendicular to the fiber axis is low, so that the fibers are weak against stress from the direction perpendicular to the fiber axis and are easily fibrillated by abrasion. For example, in the case of melt-anisotropic aromatic polyester fibers, a solid-phase polymerization reaction proceeds by subjecting the raw spun yarn obtained by melt spinning to a heat treatment, and high strength and high elastic modulus are exhibited, but this heat treatment requires a high temperature treatment, so that the surface of the fiber softens and the fibers stick to each other, and in post-processing, the stuck parts are likely to be fibrillated by abrasion. Thus, liquid crystal polymer fibers have a problem of poor abrasion resistance.

[0004] Therefore, methods for improving the abrasion resistance have been studied. For example, Patent Document 1 (JP Patent Publication 2006-336147) discloses a melt-anisotropic aromatic polyester fiber having a single fiber fineness of 0.01 to 1.5 dtex and a strength after heat treatment of 15 cN / dtex or more, in which inorganic fine particles having an average particle size of 0.001 to 1 μm are attached to the surface of the single fiber in an amount of 0.05 to 2 mass %. Patent Document 1 uses a swelling layered clay mineral as the inorganic fine particles, and attaches them to the fiber surface to prevent sticking between the single fibers.

[0005] Patent Document 2 (JP Patent Publication 2016-169464 A) discloses a liquid crystal polyester monofilament having fine irregularities on the fiber surface, a surface roughness (Ra) of the fine irregularities on the fiber surface being 0.015 μm or more and 0.100 μm or less, and a maximum diameter reduction rate of 8.0% or less. In Patent Document 2, inorganic particles (A) and a phosphoric acid compound (B) are applied to the liquid crystal polyester monofilament, and then a solid-phase polymerization reaction is carried out. The large amount of the phosphoric acid compound (B) attached promotes the scission of the molecular chain of the liquid crystal polyester present on the very surface of the fiber, resulting in a low molecular weight, and fine irregularities are formed on the fiber surface, thereby improving the abrasion resistance.

[0006] Patent Document 3 (JP 2018-3219 A) discloses a method for producing a liquid crystal polyester fiber, which comprises adding 0.001 to 0.50% by weight of inorganic particles (A) to a liquid crystal polyester, melt-spun the liquid crystal polyester fiber, coating the resulting fiber with 0.1 to 4.0% by weight of a phosphoric acid compound (B), and then solid-phase polymerization. In Patent Document 3, the inorganic particles (A) dispersed in the liquid crystal polyester fiber rise to the fiber surface as the liquid crystal polyester on the fiber surface is decomposed by the phosphoric acid compound (B) during solid-phase polymerization, thereby generating fine irregularities on the surface, thereby reducing the contact area between the fiber and the object to be rubbed, and thereby reducing friction. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2006-336147 A [Patent Document 2] JP 2016-169464 A [Patent Document 3] JP 2018-3219 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, in Patent Document 1, the swellable layered clay mineral is dispersed in a spinning oil and adhered to the fiber, but the dispersibility is insufficient. As shown in the comparative example described later, when the mineral is adhered to the fiber surface using a dispersion with insufficient dispersibility, the surface roughness of the molten anisotropic aromatic polyester fiber is small and the abrasion resistance is insufficient.

[0009] In Patent Documents 2 and 3, fine irregularities are formed by cutting the molecular chains of the liquid crystal polyester on the fiber surface with a phosphoric acid compound (B), but this method has a limit to how much the surface roughness of the fiber can be increased, and there is room for further improvement in abrasion resistance.

[0010] Therefore, the present invention is intended to solve the above problems, and has an object to provide a liquid crystal polymer fiber having excellent abrasion resistance and a method for producing the same. [Means for solving the problem]

[0011] The inventors of the present invention have investigated liquid crystal polymer fibers with excellent abrasion resistance and have surprisingly found that liquid crystal polymer fibers having a fiber surface with an arithmetic mean roughness Ra that is greater than conventional fibers and falls within a specific range have excellent abrasion resistance, which led to the completion of the present invention.

[0012] That is, the present invention can be configured in the following manner. [Aspect 1] A liquid crystal polymer fiber, the arithmetic mean roughness Ra of the fiber surface being 0.20 to 0.50 μm (preferably 0.23 to 0.48 μm, more preferably 0.25 to 0.45 μm). [Aspect 2] A liquid crystal polymer fiber according to aspect 1, wherein the coefficient of variation of the arithmetic mean roughness Ra of the fiber surface is 0.45 or less (preferably 0.40 or less, more preferably 0.35 or less, even more preferably 0.30 or less, and particularly preferably 0.25 or less). [Aspect 3] A liquid crystal polymer fiber according to embodiment 1 or 2, comprising a liquid crystal polymer containing at least one structural unit selected from the group consisting of structural units represented by the following formulas (I) to (III): -O-Ar 1 -CO- (I) -CO-Ar 2 -CO- (II) -X-Ar 3 -Y- (III) (In the formula, Ar 1 is a phenylene group, a naphthylene group, or a biphenylylene group, and Ar 2 and Ar 3 are each independently a phenylene group, a naphthylene group, a biphenylylene group, a diphenyletherdiyl group, a diphenylmethyldiyl group, or a diphenylsulfonediyl group; Ar 1 , Ar 2 and Ar 3 Each hydrogen atom of the aromatic ring may be independently substituted with a halogen atom, an alkyl group, an alkoxy group, an aryl group, an aralkyl group, an aryloxy group, or an aralkyloxy group, and each of X and Y is independently an oxygen atom or a secondary amino group (-NH-). Aspect 4 A liquid crystal polymer fiber according to any one of aspects 1 to 3, wherein at least one layered silicate mineral selected from the group consisting of smectite, vermiculite, and chlorite is attached to the fiber surface. Aspect 5 A liquid crystal polymer fiber according to any one of aspects 1 to 3, wherein a layered silicate mineral having an interlayer distance of 1.0 nm or more (preferably 1.1 nm or more, more preferably 1.2 nm or more) is attached to the fiber surface. Aspect 6 6. The liquid crystal polymer fiber according to claim 4 or 5, wherein the layered silicate mineral has a deposition amount per unit surface area of ​​0.20 to 1.20 μg / cm 2 (Preferably 0.20 to 1.00 μg / cm 2 , more preferably 0.20 to 0.90 μg / cm 2) liquid crystal polymer fiber. Aspect 7 A fiber structure comprising at least a part of the liquid crystal polymer fiber according to any one of the first to sixth aspects. Aspect 8 a step of stirring an aqueous oil solution containing a layered silicate mineral having an interlayer distance of 1.0 nm or more (preferably 1.1 nm or more, more preferably 1.2 nm or more) with a stirrer at a peripheral speed of 6 m / s or more (preferably 10 to 30 m / s, more preferably 10 to 20 m / s) to prepare a dispersion having a viscosity of 6.0 mPa s or more (preferably 6.0 to 15 mPa s, more preferably 6.0 to 10 mPa s); The amount of the layered silicate mineral attached per unit surface area on the fiber surface is 0.20 to 1.20 μg / cm 2 (Preferably 0.20 to 1.00 μg / cm 2 , more preferably 0.20 to 0.90 μg / cm 2 and applying the dispersion to the liquid crystal polymer fibers so that the dispersion becomes a liquid crystal polymer fiber. Aspect 9 A method for producing a liquid crystalline polymer fiber according to embodiment 8, further comprising the steps of: applying the dispersion to the liquid crystalline polymer fiber; and heat treating the liquid crystalline polymer fiber and / or heat stretching the liquid crystalline polymer fiber. Aspect 10 10. The method for producing liquid crystal polymer fibers according to aspect 8 or 9, wherein the aqueous oil agent contains the layered silicate mineral in an amount of 0.1 to 10 wt % (preferably 0.3 to 8 wt %, and more preferably 0.5 to 5 wt %). Aspect 11 A method for producing liquid crystal polymer fibers according to any one of aspects 8 to 10, wherein in the dispersion preparation step, the stirring time is 30 minutes or more (preferably 2 hours or more, more preferably 8 hours or more, and even more preferably 12 hours or more). Effect of the Invention

[0013] The liquid crystal polymer fiber of the present invention has excellent abrasion resistance. Moreover, the manufacturing method of the present invention can increase the arithmetic mean roughness Ra of the surface to a specific range without changing the portion of the liquid crystal polymer fiber that is composed of the liquid crystal polymer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] [Liquid crystal polymer fiber] The liquid crystal polymer fiber includes a liquid crystal polymer. Examples of the liquid crystal polymer include a thermotropic liquid crystal polymer that exhibits liquid crystallinity in a molten state and a lyotropic liquid crystal polymer that exhibits liquid crystallinity in a solution state. Examples of the thermotropic liquid crystal polymer include a molten anisotropic aromatic polyester. Examples of the lyotropic liquid crystal polymer include a wholly aromatic polyamide and a polybenzazole.

[0015] The melt-anisotropic aromatic polyester is, for example, composed of structural units derived from aromatic diol, aromatic dicarboxylic acid, aromatic hydroxycarboxylic acid, etc., and the structural units derived from aromatic diol, aromatic dicarboxylic acid, aromatic hydroxycarboxylic acid, etc. are not particularly limited in chemical structure as long as they do not impair the effects of the present invention. In addition, the melt-anisotropic aromatic polyester may be a melt-anisotropic aromatic polyester amide containing structural units derived from aromatic diamine, aromatic hydroxyamine, or aromatic aminocarboxylic acid, so long as they do not impair the effects of the present invention. For example, examples of preferred structural units are shown in Table 1.

[0016] [Table 1]

[0017] In the structural units in Table 1, m is an integer of 0 to 2, and Y in the formula, in the range of 1 to the maximum number of possible substitution, each independently represents 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., an alkyl group having 1 to 4 carbon atoms 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, a 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), an aralkyloxy group (e.g., a benzyloxy group), etc.).

[0018] More preferred structural units include the structural units described in Examples (1) to (20) in Tables 2, 3, and 4. When the structural unit in the formula is a structural unit that can exhibit multiple structures, two or more of such structural units may be combined and used as a structural unit that constitutes the polymer.

[0019] [Table 2]

[0020] [Table 3]

[0021] [Table 4]

[0022] In the structural units of Tables 2, 3 and 4, n is an integer of 1 or 2, and each structural unit n=1, 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., an alkyl group having 1 to 4 carbon atoms 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.), etc. Among these, a hydrogen atom, a chlorine atom, a bromine atom, or a methyl group is preferred.

[0023] Furthermore, examples of Z include substituents represented by the following formulas.

[0024] [ka]

[0025] The melt anisotropic aromatic polyester is preferably a copolymer containing at least a structural unit (A) derived from hydroxybenzoic acid and / or a structural unit (B) derived from hydroxynaphthoic acid. For example, the structural unit (A) is a structural unit derived from 4-hydroxybenzoic acid represented by the following formula (A), and the structural unit (B) is a structural unit derived from 6-hydroxy-2-naphthoic acid represented by the following formula (B).

[0026] [ka]

[0027] [ka]

[0028] The melting point (hereinafter sometimes referred to as Mp0) of the melt anisotropic aromatic polyester 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 main absorption peak temperature observed when measured by a differential scanning calorimeter (DSC) in accordance with the JIS K 7121 test method. Specifically, 4 to 6 mg of a sample is taken and sealed in an aluminum pan in a DSC device, and then 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 (for example, 25°C) at a rate of 10°C / min. If no clear peak appears in the first run of DSC measurement due to the type of polymer, the polymer should be heated at 50°C / min to a temperature 50°C higher than the expected flow temperature, completely melted at that temperature for 3 minutes, then cooled to 50°C at a rate of 80°C / min, and then the endothermic peak should be measured at a heating rate of 10°C / min.

[0029] The melt-melt anisotropic aromatic polyester may be mixed with a thermoplastic polymer such as polyethylene terephthalate, modified polyethylene terephthalate, polyolefin, polycarbonate, polyamide, polyphenylene sulfide, polyether ether ketone, fluororesin, etc., within the scope of not impairing the effects of the present invention. In addition, various additives such as inorganic substances such as titanium oxide, kaolin, silica, barium oxide, etc., colorants such as carbon black, dyes and pigments, antioxidants, ultraviolet absorbers, light stabilizers, etc. may be mixed.

[0030] The wholly aromatic polyamide is composed of, for example, constituent units derived from aromatic diamines, aromatic dicarboxylic acids, aromatic aminocarboxylic acids, etc., and the constituent units derived from aromatic diamines, aromatic dicarboxylic acids, and aromatic aminocarboxylic acids are not particularly limited in terms of their chemical constitution, so long as the effects of the present invention are not impaired.

[0031] For example, examples of aromatic diamines include p-phenylenediamine, m-phenylenediamine, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl methane, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, etc. In addition, examples of derivatives in which hydrogen atoms in the aromatic rings of these aromatic diamines are substituted with halogen atoms, alkyl groups, alkoxy groups, aryl groups, aralkyl groups, aryloxy groups, aralkyloxy groups, etc. include 2-chloro-p-phenylenediamine, 2,5-dichloro-p-phenylenediamine, 2,6-dichloro-p-phenylenediamine, 2-chloro-m-phenylenediamine, 4-chloro-m-phenylenediamine, 2-methyl-p-phenylenediamine, 2-methyl-m-phenylenediamine, 4-methyl-m-phenylenediamine, etc.

[0032] Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, etc. In addition, examples of derivatives in which hydrogen atoms on the aromatic rings of these aromatic dicarboxylic acids are substituted with halogen atoms, alkyl groups, alkoxy groups, phenyl groups, etc. include 2-chloroterephthalic acid, 2,5-dichloroterephthalic acid, 2,6-dichloroterephthalic acid, 3-chloroisophthalic acid, 3-methoxyisophthalic acid, etc.

[0033] The wholly aromatic polyamide may preferably be poly-p-phenylene terephthalamide containing structural units derived from p-phenylenediamine and structural units derived from terephthalic acid; poly-m-phenylene isophthalamide containing structural units derived from m-phenylenediamine and structural units derived from isophthalic acid; or copoly-p-phenylene-3,4'-oxydiphenylene terephthalamide containing structural units derived from p-phenylenediamine and structural units derived from 3,4'-diaminodiphenyl ether as aromatic diamines, and structural units derived from terephthalic acid as aromatic dicarboxylic acid.

[0034] Polybenzazole is a polymer having a benzazole-based heteroaromatic ring in the main chain, and examples thereof include polybenzoxazole having a benzoxazole ring, polybenzothiazole having a benzothiazole ring, and polybenzimidazole having a benzimidazole ring. Polybenzazole preferably has a structural unit in which a benzazole-based heteroaromatic ring is bonded to an aromatic group, and examples of the aromatic group include a phenylene group, a biphenylene group, and a naphthylene group. In addition, examples of the aromatic ring bonded to the azole-based heteroaromatic ring of the benzazole-based heteroaromatic ring include a benzene ring, a pyridine ring, and a naphthalene ring, and the hydrogen atoms of these aromatic rings may be substituted with halogen atoms, alkyl groups, etc.

[0035] The polybenzazole may preferably be poly(p-phenylene benzobisoxazole) or poly(p-phenylene benzobisthiazole).

[0036] Among these liquid crystal polymers, melt anisotropic aromatic polyesters and wholly aromatic polyamides are preferred. For example, the liquid crystal polymer may contain at least one structural unit selected from the group consisting of structural units (structural units (I) to (III)) represented by the following formulas (I) to (III). -O-Ar 1 -CO- (I) -CO-Ar 2 -CO- (II) -X-Ar 3 -Y- (III) (In the formula, Ar 1 is a phenylene group, a naphthylene group, or a biphenylylene group, and Ar 2 and Ar 3 are each independently a phenylene group, a naphthylene group, a biphenylylene group, a diphenyletherdiyl group, a diphenylmethyldiyl group, or a diphenylsulfonediyl group; Ar 1 , Ar 2 and Ar 3Each hydrogen atom in the aromatic ring may be independently substituted with a halogen atom, an alkyl group, an alkoxy group, an aryl group, an aralkyl group, an aryloxy group, or an aralkyloxy group, and each of X and Y is independently an oxygen atom or a secondary amino group (-NH-).

[0037] The structural unit (I) is a structural unit derived from an aromatic hydroxycarboxylic acid, the structural unit (II) is a structural unit derived from an aromatic dicarboxylic acid, and the structural unit (III) is a structural unit derived from an aromatic diol (X and Y are oxygen atoms), an aromatic diamine (X and Y are secondary amino groups) or an aromatic hydroxyamine (one of X and Y is an oxygen atom, and the other is a secondary amino group).

[0038] The liquid crystal polymer may contain one or more of the structural units (I) to (III) respectively. The total content of the structural units (I) to (III) in the liquid crystal polymer may be, for example, 90 mol % or more, preferably 95 mol % or more, more preferably 99 mol % or more, and even more preferably 100 mol %, based on the total amount of all the structural units.

[0039] The liquid crystal polymer may be a melt-type anisotropic aromatic polyester having the structural unit (I) as a main component, a melt-type anisotropic aromatic polyester having structural units (I) to (III), or a wholly aromatic polyamide having structural units (II) and (III).

[0040] For example, the liquid crystal polymer may be a melt-dispersible anisotropic aromatic polyester having two or more kinds of structural units (I). As the structural unit (I), Ar 1Examples of the structural unit include a 1,4-phenylene group (structural unit (A) derived from 4-hydroxybenzoic acid) and a 2,6-naphthylene group (structural unit (B) derived from 6-hydroxy-2-naphthoic acid). Preferably, the structural unit may be a copolymer containing the structural unit (A) and the structural unit (B). For example, from the viewpoint of improving melt moldability, the ratio (A) / (B) of the structural unit (A) to the structural unit (B) may be in the range of preferably 9 / 1 to 1 / 1, more preferably 7 / 1 to 1 / 1, and even more preferably 5 / 1 to 1 / 1.

[0041] The total of the structural units (A) and (B) may be, for example, 65 mol % or more, more preferably 70 mol % or more, and even more preferably 80 mol % or more, based on all structural units. The melt-dispersible aromatic polyester may contain 4 to 45 mol % of the structural unit (B) based on all structural units.

[0042] The melt-type anisotropic aromatic polyester may contain the structural unit (A) in an amount of 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, based on the total structural units. The upper limit of the content of the structural unit (A) in the melt-type anisotropic aromatic polyester is not particularly limited, but may be, for example, 90 mol% or less, preferably 88 mol% or less, and more preferably 85 mol% or less.

[0043] The liquid crystal polymer may be a melt anisotropic aromatic polyester having structural units (I) to (III), and for example, a copolymer containing a structural unit (I) derived from an aromatic hydroxycarboxylic acid, i.e., a structural unit (A) derived from 4-hydroxybenzoic acid and / or a structural unit (B) derived from 6-hydroxy-2-naphthoic acid, a structural unit (II) derived from at least one type of aromatic dicarboxylic acid, and a structural unit (III) derived from at least one type of aromatic diol and / or aromatic hydroxyamine is preferred.

[0044] The structural unit (II) is Ar 2However, preferred are 1,4-phenylene group constituent units (constituent units derived from terephthalic acid), 1,3-phenylene group constituent units (constituent units derived from isophthalic acid), 2,6-naphthylene group constituent units (constituent units derived from 2,6-naphthalene dicarboxylic acid), 4,4'-biphenylylene group constituent units (constituent units derived from 4,4'-biphenyldicarboxylic acid), and diphenylether-4,4'-diyl group constituent units (constituent units derived from diphenylether-4,4'-dicarboxylic acid).

[0045] The aromatic diol structural unit (III) is Ar 3 However, preferred are 1,4-phenylene group structural units (structural units derived from hydroquinone), 4,4'-biphenylylene group structural units (structural units derived from 4,4'-dihydroxybiphenyl), phenyl-1,4-phenylene group structural units (structural units derived from phenylhydroquinone), and diphenylether-4,4'-diyl group structural units (structural units derived from 4,4'-dihydroxydiphenyl ether).

[0046] The aromatic hydroxylamine structural unit (III) is Ar 3 However, a structural unit which is a 1,4-phenylene group (a structural unit derived from 4-aminophenol) and a structural unit which is a 4,4'-biphenylylene group (a structural unit derived from 4-amino-4'-hydroxybiphenyl) are preferred.

[0047] The content of the structural unit (I) in the melt-type anisotropic aromatic polyester may be 20 to 80 mol %, preferably 30 to 75 mol %, and more preferably 40 to 70 mol %, based on the total amount of all structural units.

[0048] The content of the structural unit (II) in the melt-type anisotropic aromatic polyester may be 10 to 40 mol %, preferably 12.5 to 35 mol %, and more preferably 15 to 30 mol %, based on the total amount of all structural units.

[0049] The content of the structural unit (III) in the melt-type anisotropic aromatic polyester may be 10 to 40 mol %, preferably 12.5 to 35 mol %, and more preferably 15 to 30 mol %, based on the total amount of all structural units.

[0050] From the viewpoint of easily increasing the molecular weight of the molten anisotropic aromatic polyester and improving its mechanical properties, the molar ratio of the content of the structural unit (II) to the content of the structural unit (III), (II) / (III), may be 90 / 100 to 100 / 90, preferably 95 / 100 to 100 / 95, more preferably 98 / 100 to 100 / 98, and even more preferably 100 / 100.

[0051] The liquid crystal polymer may be a wholly aromatic polyamide having structural units (II) and (III), and for example, a copolymer containing structural units (II) derived from an aromatic dicarboxylic acid, such as structural units derived from terephthalic acid and / or structural units derived from isophthalic acid, and structural units (III) derived from at least one aromatic diamine is preferred.

[0052] The aromatic diamine structural unit (III) is Ar 3 However, preferred are a 1,4-phenylene group structural unit (a structural unit derived from p-phenylenediamine), a 1,3-phenylene group structural unit (a structural unit derived from m-phenylenediamine), a diphenylether-3,4'-diyl group structural unit (a structural unit derived from 3,4'-diaminodiphenyl ether), a diphenylether-4,4'-diyl group structural unit (a structural unit derived from 4,4'-diaminodiphenyl ether), a diphenylmethyl-4,4'-diyl group structural unit (a structural unit derived from 4,4'-diaminodiphenylmethane), and a diphenylsulfone-3,4'-diyl group structural unit (a structural unit derived from 3,4'-diaminodiphenyl sulfone).

[0053] The liquid crystal polymer fibers may contain 50% or more by weight of liquid crystal polymer, preferably 80% or more by weight, more preferably 90% or more by weight, even more preferably 95% or more by weight, and even more preferably 98% or more by weight.

[0054] The liquid crystal polymer fiber has an arithmetic mean roughness Ra of the fiber surface of 0.20 to 0.50 μm. The liquid crystal polymer fiber has fine irregularities on its surface and has a specific surface roughness, so that the contact area with the friction object can be reduced and the wear resistance is excellent. If the arithmetic mean roughness Ra of the surface is too small, the contact area with the friction object increases, and the amount of wear increases, so that the wear resistance is insufficient. On the other hand, if the arithmetic mean roughness Ra of the surface is too large, the friction resistance is concentrated on the convex parts of the fiber surface, and the fiber is easily worn, so that the wear resistance is insufficient. The arithmetic mean roughness Ra of the fiber surface may be preferably 0.23 to 0.48 μm, more preferably 0.25 to 0.45 μm. The arithmetic mean roughness Ra is an index of roughness in the height direction measured in accordance with JIS B 0601:2001, and is an index of the roughness in the roughness curve of the reference length, and is expressed as the average value of the absolute value of the deviation from the average line to the roughness curve. In this specification, the arithmetic average roughness Ra is a value measured from the profile curve of the surface of a single fiber in the fiber axial direction by the method described in the Examples below.

[0055] The liquid crystal polymer fiber may have a coefficient of variation of the arithmetic mean roughness Ra of the fiber surface of 0.45 or less. By making the degree of unevenness of the liquid crystal polymer fiber surface more uniform, the wear resistance of the fiber as a whole can be improved, and wear when contacting a guide or the like during processing such as weaving can be suppressed, thereby improving process passability. The coefficient of variation of the arithmetic mean roughness Ra of the fiber surface may be preferably 0.40 or less, more preferably 0.35 or less, even more preferably 0.30 or less, and particularly preferably 0.25 or less. The coefficient of variation of the arithmetic mean roughness Ra of the fiber surface can be calculated by the standard deviation of the arithmetic mean roughness Ra / the arithmetic mean roughness Ra (average value), and is a value measured by the method described in the examples described later.

[0056] The liquid crystal polymer fiber is preferably one in which at least one layered silicate mineral selected from the group consisting of smectite, vermiculite, and chlorite (chlorite) is attached to the fiber surface. In this case, the liquid crystal polymer fiber is composed of a fiber main body mainly composed of a liquid crystal polymer and a surface attachment part containing a layered silicate mineral formed so as to cover the fiber main body, and the arithmetic mean roughness Ra of the fiber surface is affected by the state of the surface attachment part. These layered silicate minerals can be cleaved to a high degree, probably because of the large interlayer distance, so that by attaching such layered silicate minerals to the fiber surface, finer irregularities can be formed, and the arithmetic mean roughness Ra can be increased. Smectite, vermiculite, and chlorite respectively indicate the group names of layered silicate minerals (smectite group, vermiculite group, and chlorite group), and are not particularly limited as long as they are layered silicate minerals belonging to these groups. Among these, smectite is preferred from the viewpoint of having swelling properties and being easier to cleave.

[0057] The liquid crystal polymer fiber preferably has a layered silicate mineral with an interlayer distance of 1.0 nm or more attached to the fiber surface. The layered silicate mineral has a basic layer formed by a combination of a tetrahedral sheet in which oxygen tetrahedra centered on silicon ions (which may be substituted with aluminum ions, etc.) are two-dimensionally bonded, and an octahedral sheet in which oxygen octahedra centered on metal ions such as aluminum and magnesium are two-dimensionally connected in a network, and has a layered structure in which such basic layers are stacked. The interlayer distance of the layered silicate mineral is the average distance between the basic layers, and can be measured as the interlayer distance d(001) from the diffraction peak of the (001) plane by small angle X-ray scattering (SAXS). A layered silicate mineral with an interlayer distance of 1.0 nm or more is preferable because it can be highly cleaved. The interlayer distance of the layered silicate mineral may be preferably 1.1 nm or more, more preferably 1.2 nm or more, and the upper limit may be, for example, 10 nm or less.

[0058] Examples of layered silicate minerals with an interlayer distance of 1.0 nm or more include smectite, vermiculite, chlorite, and mixed-layer minerals in which a plurality of crystal structures are mixed.

[0059] In liquid crystal polymer fibers, the amount of layered silicate minerals attached per unit surface area of ​​the fiber surface is 0.20 to 1.20 μg / cm 2 The arithmetic average roughness Ra can be adjusted by adjusting the amount of a specific layered silicate mineral attached to the fiber surface. The amount of layered silicate mineral attached per unit surface area of ​​the fiber surface is preferably 0.20 to 1.00 μg / cm. 2 , more preferably 0.20 to 0.90 μg / cm 2 In this specification, the amount of layered silicate mineral attached per unit surface area of ​​the fiber surface refers to the amount of layered silicate mineral attached based on the surface area of ​​the fiber calculated from the fineness, assuming that the fiber surface is flat and free of irregularities and the fiber cross section is a perfect circle, and is a value measured by the method described in the Examples below.

[0060] The layered silicate mineral is preferably not dispersed in the fiber body constituting the fiber itself, but is fixed to the fiber body as a surface-attached portion so as to cover the fiber body. When the layered silicate mineral is fixed to the fiber surface, it is possible to prevent the layered silicate mineral from falling off even when ultrasonic cleaning is performed with an aqueous solution containing a surfactant.

[0061] The liquid crystal polymer fiber may be a non-composite fiber or a composite fiber. In particular, it is preferable that the liquid crystal polymer is present on the surface of the fiber main body.

[0062] The single fiber fineness of the liquid crystal polymer fiber can be appropriately selected depending on the application, etc., and may be, for example, 50 dtex or less, preferably 15 dtex or less, more preferably 10 dtex or less. The lower limit of the single fiber fineness is not particularly limited, but may be, for example, about 0.01 dtex. The single fiber fineness is a value measured by the method described in the examples below.

[0063] The liquid crystal polymer fiber may be a monofilament or a multifilament. In the case of a multifilament, the number of filaments can be appropriately selected depending on 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.

[0064] The total fineness of the liquid crystal polymer fiber can be appropriately selected depending on the application, etc., and may be, for example, 50,000 dtex or less, preferably 10,000 dtex or less, more preferably 5,000 dtex or less, and further preferably 2,000 dtex or less. The lower limit of the total fineness is not particularly limited, but may be, for example, about 1 dtex.

[0065] [Method of manufacturing liquid crystal polymer fiber] The method for producing liquid crystal polymer fibers may include a step of adding a layered silicate mineral having an interlayer distance of 1.0 nm or more to an aqueous oil solution, stirring the solution with a stirrer at a peripheral speed of 6 m / s or more to prepare a dispersion having a viscosity of 6.0 mPa s or more, and a step of applying the dispersion to liquid crystal polymer fibers.

[0066] By applying a dispersion of layered silicate mineral to liquid crystal polymer fiber, unevenness can be formed on the fiber surface. The inventors of the present invention have found that when a specific layered silicate mineral is used, the arithmetic mean roughness Ra of the applied fiber surface varies depending on the dispersion state of the layered silicate mineral in the dispersion. When an oil-based aqueous solution is used as a dispersion medium, layered silicate mineral is prone to aggregation and is difficult to disperse, but it has been found that by stirring at a very high peripheral speed and applying high shear, the layered silicate mineral can be highly cleaved, and a dispersion with good dispersibility can be obtained. By using a dispersion prepared by dispersing a specific amount of such layered silicate mineral in an oil-based aqueous solution, it is possible to adjust the arithmetic mean roughness Ra of the fiber surface of the liquid crystal polymer fiber.

[0067] In the dispersion preparation step, the layered silicate mineral may be added to the aqueous oil agent liquid and stirred with a stirrer at a peripheral speed of 6 m / s or more. By using a stirrer capable of stirring at such a high peripheral speed, the layered silicate mineral can be highly cleaved, and the dispersibility in the aqueous oil agent liquid can be improved. The peripheral speed of the stirrer may be preferably 10 to 30 m / s, more preferably 10 to 20 m / s. The stirrer is not particularly limited as long as it can stir at the above peripheral speed, and for example, a high-speed rotation shear type stirrer such as a homogenizer or a homomixer can be used.

[0068] The stirring time may be 30 minutes or more, preferably 2 hours or more, more preferably 8 hours or more, and further preferably 12 hours or more, from the viewpoint of improving the retention of the dispersed state and applying the agent more uniformly to the fiber surface. The upper limit of the stirring time is not particularly limited, but may be, for example, 24 hours or less from the viewpoint of improving productivity.

[0069] The layered silicate mineral may be added to the aqueous oil solution so as to be contained in an amount of 0.1 to 10 wt%. The content of the layered silicate mineral refers to the ratio of the amount of the layered silicate mineral to the total amount of the aqueous oil solution and the layered silicate mineral. By adjusting the content of the layered silicate mineral, the viscosity of the dispersion can be adjusted and the amount of the layered silicate mineral attached to the fiber surface can be adjusted. The layered silicate mineral may be added to the aqueous oil solution so as to be contained in an amount of preferably 0.3 to 8 wt%, more preferably 0.5 to 5 wt%.

[0070] The interlayer distance of the layered silicate mineral added to the aqueous oil agent liquid may be preferably 1.1 nm or more, and more preferably 1.2 nm or more.

[0071] The layered silicate mineral added to the aqueous oil agent liquid may be at least one layered silicate mineral selected from the group consisting of smectite, vermiculite, and chlorite.

[0072] The layered silicate mineral to be added to the aqueous oil agent liquid may have a median diameter of 0.01 to 30 μm, preferably 0.1 to 30 μm, more preferably 1 to 25 μm, and even more preferably 3 to 25 μm. The median diameter is the particle diameter at which the cumulative volume in the particle diameter distribution is 50%.

[0073] The prepared dispersion may have a viscosity of 6.0 mPa·s or more. When dispersed by the above method and has such a viscosity, the cleaved layered silicate mineral is less likely to aggregate and can maintain a dispersed state for a long period of time, so that it can be stably applied to the liquid crystal polymer fiber. In order to adhere the layered silicate mineral more uniformly, the viscosity of the dispersion may be preferably 6.0 to 15 mPa·s, more preferably 6.0 to 10 mPa·s.

[0074] The dispersion preferably has thixotropy. Thixotropy is a property in which the viscosity is relatively high when left at rest without applying stress, the viscosity decreases when shear stress is applied, and the viscosity increases over time and returns to the original value when the application of shear stress is stopped. When the dispersion has thixotropy, if the dispersion is applied while the liquid crystal polymer fiber is running, the viscosity decreases due to shear stress, so that the dispersion can be attached to the fiber surface more uniformly, and after attachment, the viscosity increases and the dispersion can be fixed to the fiber surface. The thixotropy of the dispersion may be determined by checking the viscosity behavior of the dispersion accompanying the stirring in the preparation process. That is, it can be determined by checking the viscosity behavior in which the viscosity of the dispersion decreases during stirring and increases after stirring is stopped. The prepared dispersion preferably has thixotropic stability from the viewpoint of stably attaching to the fiber surface, and when the thixotropic stability is high, the viscosity of the prepared dispersion increases, so that the retention of the dispersed state can be improved. For example, the layered silicate mineral is preferably in a dispersed state for 8 hours or more when the dispersion liquid after preparation is allowed to stand, and more preferably in a dispersed state for 24 hours or more.

[0075] The oil agent contained in the aqueous oil agent liquid in which the layered silicate mineral is dispersed can be a known oil agent used for fibers, and examples thereof include phosphoric acid compounds. The aqueous oil agent liquid may be an aqueous oil agent solution in which an oil agent is dissolved in an aqueous medium, or an aqueous oil agent dispersion in which an oil agent is dispersed in an aqueous medium. Examples of the aqueous medium include water and hydrophilic organic solvents, and examples of the hydrophilic organic solvent include alcohols such as methanol, ethanol, and propylene glycol. The aqueous oil agent liquid may contain 0.1 to 10 wt%, preferably 0.3 to 5 wt%, and more preferably 0.5 to 3 wt% of the oil agent.

[0076] In the dispersion applying step, the dispersion prepared above is applied to the liquid crystal polymer fiber. The application method is not particularly limited, and examples thereof include known application methods such as impregnation treatment, discharge treatment, coating treatment, and immersion squeezing treatment. It is preferable to apply the dispersion to the running liquid crystal polymer fiber using an oiling guide such as an oiling roller or a glass nozzle.

[0077] The dispersion liquid may be applied while the spun raw yarn is being wound, or may be applied when the raw yarn that has been spun and wound is being rewound. The dispersant may be applied once or multiple times. The liquid crystal polymer fiber may be spun by a known liquid crystal spinning method depending on the type of the fiber. For example, melt-anisotropic aromatic polyester fiber can be obtained by melt spinning, and wholly aromatic polyamide fiber or polybenzazole fiber can be obtained by solution spinning such as dry spinning, wet spinning, or dry-wet spinning.

[0078] After the dispersion is applied, the liquid crystal polymer fiber may be subjected to heat treatment and / or heat drawing. The dispersion is preferably applied before heat treatment or heat drawing. The mechanical properties of the liquid crystal polymer fiber can be improved by heat treatment or heat drawing of the raw spun yarn. However, heat treatment or heat drawing requires exposure to high temperatures, which causes the single fibers to stick together. Therefore, sticking can be suppressed by attaching a layered silicate mineral to the fiber surface before heat treatment or heat drawing. Then, by performing heat treatment or heat drawing in a state in which the layered silicate mineral is attached to the fiber surface, the layered silicate mineral can be fixed to the fiber surface. The heat treatment and / or heat drawing can be performed by a known method depending on the type of liquid crystal polymer fiber.

[0079] For example, by subjecting the raw spun yarn of the melt-anisotropic aromatic polyester fiber to heat treatment, it is possible to proceed with solid-phase polymerization and improve the strength and elastic modulus of the fiber. The heat treatment method is not particularly limited, and may be, for example, a batch-type heat treatment or a continuous heat treatment by conveying. In the batch-type heat treatment, for example, the heat treatment may be performed in a state where the yarn is wound around a bobbin in a packaged form, in a skein form, or in a tow form, and it is preferable to perform the heat treatment in a packaged form in terms of simplifying the equipment and improving productivity. In the case of continuous heat treatment by conveying, the conveying method may be either contact conveying (for example, a conveyor system, a support roll system, or a heat treatment system in the form of a heated roller) or non-contact conveying (a roll-to-roll system).

[0080] The heat treatment can be carried out by a known method, for example, atmospheric heating, contact heating, etc. The atmosphere is preferably air, an inert gas (e.g., nitrogen, argon), or a combination thereof. The heat treatment can also be carried out under reduced pressure.

[0081] The heat treatment temperature may be 230°C or higher, and from the viewpoint of efficient strength improvement, it may be preferably 240°C or higher, more preferably 250°C or higher. The heat treatment temperature may be lower than the melting point of the raw spinning yarn to prevent melting. Since the melting point of the molten anisotropic aromatic polyester fiber increases with the progress of solid-state polymerization, the initial heat treatment temperature may be lower than the melting point of the raw spinning yarn. From the viewpoint of efficient strength improvement, the heat treatment temperature may be increased stepwise according to the progress of solid-state polymerization, and the heat treatment may be performed at a temperature higher than the melting point at the time of the heat treatment (the melting point of the raw spinning yarn).

[0082] The heat treatment time can be appropriately set depending on the heat treatment method and heat treatment temperature. For example, it can be set in the range of 15 minutes to 30 hours, preferably 2 to 24 hours, and more preferably 3 to 20 hours. The heat treatment time here refers to the holding time at a predetermined heat treatment temperature.

[0083] For example, the raw spun yarn of the wholly aromatic polyamide fiber may be subjected to heat drawing and, if necessary, heat treatment. The heat drawing may be performed using a heating bath, hot steam spraying, a roller heater, a contact plate heater, a non-contact plate heater, etc. The heat treatment may be performed by continuous heat treatment by conveying.

[0084] [Fiber structure] The liquid crystal polymer fiber can be used in various applications as a fiber structure containing at least a part of the liquid crystal polymer fiber. The fiber structure containing the liquid crystal polymer fiber can be used in any fiber form such as staple fiber, short cut fiber, filament yarn, spun yarn, string-like material, rope, etc. Also, it can be used as various fabrics such as nonwoven fabrics, woven fabrics, knitted fabrics, etc. using the liquid crystal polymer fiber. Such fibers and fabrics can be produced using the liquid crystal polymer fiber by a known method.

[0085] The fiber structure may be a combination of liquid crystal polymer fibers and other fibers, as long as the effect of the present invention is not impaired. For example, composite fibers using liquid crystal polymer fibers and other fibers (e.g., mixed yarns in which liquid crystal polymer fibers are mixed with other fibers) can be used. Also, composite fabrics using liquid crystal polymer fibers and other fibers (e.g., mixed fabrics in which liquid crystal polymer fibers are mixed with other fibers, and laminates of fabrics made of liquid crystal polymer fibers and fabrics made of other fibers) can be used.

[0086] Liquid crystal polymer fibers can be used in various fiber structures for various applications such as general industrial materials, civil engineering and construction materials, various reinforcing materials, electrical and electronic component materials, various fiber products, etc. For example, they can be used in advanced processed products such as tension members (electric wires, optical fibers, umbilical cables, heater wire core threads, cords for various electrical products such as earphone cords, etc.), sail cloth, ropes (marine, mountain climbing, cranes, yachts, tugs, etc.), ropes, land nets, slings, lifelines, fishing lines, sewing threads, screen cords, fishing nets, longlines, geogrids, protective gloves, ripstop protective clothing and outdoor clothing, rider suits, sports rackets, guts, medical catheter reinforcement materials, suture threads, screen gauze, filters, base fabrics for printed circuit boards, mesh-like conveyor belts, papermaking belts, dryer canvases, airships, balloons, airbags, speaker cones, reinforcement materials for various hoses and pipes, and reinforcement materials for rubber and plastics such as tires and conveyor belts. EXAMPLES

[0087] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following examples and comparative examples, various physical properties were measured by the following methods.

[0088] (Melting point of resin chips (granular moldings)) The melting point was determined as the main absorption peak temperature observed by measuring using a differential scanning calorimeter (DSC; Shimadzu Corporation's "DSC60A Plus") in accordance with JIS K 7121. Specifically, 4 to 6 mg of the sample was placed in an aluminum pan and sealed in the DSC apparatus, and then nitrogen was passed as a carrier gas at a flow rate of 200 mL / min, and the endothermic peak derived from the molten anisotropic aromatic polyester was measured when the temperature was raised from 25°C at a rate of 10°C / min.

[0089] (Interlayer distance of layered silicate minerals) The interlayer distance of layered silicate minerals was measured using a small-angle X-ray scattering device (Rigaku Corporation, "NANO-VIEWER"). The X-ray source was a CuKα source of 200 kV and 30 mA, and the detector was a two-dimensional CCD detector. The distance between the sample and the detector (camera length) was 700 mm. The sample was an aqueous dispersion of layered silicate minerals dispersed in water to a content of 7.0 wt%. The sample was sealed in a metal assembly cell with a 2 mm optical path length and a polyacetate or Kapton film window, and placed in the sample holder. The measurement time was typically 30 minutes. The data obtained was corrected taking into account the dark signal of the detector, scattering from the dispersion medium and window material, and the transmittance of X-rays, and the interlayer distance was calculated from the position (2θ) of the diffraction peak of the (001) plane.

[0090] (Median diameter of layered silicate minerals) Using a laser diffraction / scattering particle size distribution analyzer (HORIBA, LTD. "LA-950V2") and a dry unit as an accessory, the particle size distribution was measured while the layered silicate mineral was dispersed with compressed air. The refractive index of the sample was 1.700-0.000i, and the refractive index of the dispersion medium (air) was 1.000. The median size of the layered silicate mineral was measured from the obtained particle size distribution.

[0091] (Viscosity of dispersion) A viscometer (Rheosys "PN200100") was used to measure the viscosity of the dispersions prepared in the examples and comparative examples by attaching a rotating part according to the viscosity. 12 mL of the dispersion (until the rotating part was completely immersed) was poured in, and the device was operated at a constant rotation speed of 1000 / s and a temperature of 20±0.1°C for 50 seconds, after which the average value of the measured values ​​over 10 seconds was measured as one point of viscosity data (one point every minute). This measurement was continued for 10 minutes, and viscosity data was measured at 10 points, and this average value was taken as the viscosity of the dispersion.

[0092] (Thixotropic stability of dispersion) The presence or absence of thixotropy in the dispersions prepared in the Examples and Comparative Examples was determined by visually checking whether the fluidity of the dispersions after stirring was lowered when the dispersions were left to stand than when they were being stirred. After the dispersions after stirring were left to stand for a predetermined time, a laser beam was irradiated to visually check whether the dispersion medium and the layered silicate mineral were separated. If they were not separated, it was determined that the layered silicate mineral had not settled and maintained a dispersed state. The stability of the thixotropy of the dispersions was evaluated according to the following criteria. : The dispersion state was maintained even after 24 hours. ○: The layered silicate mineral and the dispersion medium separated within 8 hours or more but less than 24 hours. △: The layered silicate mineral and the dispersion medium separated in less than 8 hours.

[0093] (Arithmetic mean roughness Ra) In accordance with JIS B 0601:2001, the arithmetic mean roughness Ra of the fiber surface of the liquid crystal polymer fiber was measured at a magnification of 3000x (objective 150x x 20) using a laser microscope manufactured by Keyence Corporation (controller unit "VK-X200", measurement unit "VK-X210") using the following method.

[0094] A liquid crystal polymer fiber thread with a length of 1m or more was taken, and a total of 10 samples with a length of 7cm were taken from one end of the thread at 3cm intervals. In order to remove foreign matter from the fiber surface of the samples, the samples were immersed in an aqueous solution of 2.0% by weight of sodium dodecylbenzenesulfonate in pure water and ultrasonically cleaned for 20 minutes at room temperature. After cleaning, the samples were rinsed with water and air-dried. After air-drying, the samples were placed on a slide glass (2.6cm long x 7.6cm wide) so that the samples did not overlap each other, and both ends of the sample were fixed with cellophane tape. The slide glass with the samples fixed was set on the stage of a laser microscope, and the center of each sample (within ±5mm of the center of the sample) was observed.

[0095] The observation application (VK-H1XV) was started on the PC, and in the "image observation mode," the low-magnification objective lens was used to first focus on the center of one target sample, and then the objective lens was changed to 150x and refocused. At this time, the slide glass or stage was adjusted so that the horizontal axis direction of the observation field was parallel to the fiber axis direction. Then, in the "shape measurement mode" of the observation application (VK-H1XV), "expert" was selected, and the brightness of the laser was adjusted while the laser image was displayed, and the upper and lower limits of the measurement range (height direction) were set so that the top end and both sides of the target sample in the observation field were included. The measurement mode was set to "surface shape," the measurement size to "high resolution," and the measurement quality to "high accuracy." The RPD (Real Peak Detection) check box was checked, and "Start measurement" was selected, and the obtained measurement results (image file) were saved. In this case, the measurement pitch was set to 0.080 μm. After that, the analysis application (VK-H1XA) was started on the PC, the obtained image file was opened, the number of digits to be displayed was set to two decimal places, and "Line roughness" was selected from the "Measurement analysis" menu to display the line roughness measurement window. "Parallel line" was selected from the measurement lines, and a measurement line was drawn in the center of the fiber so that the measurement line was parallel to the fiber axis direction on the image. An inclination correction (straight line (automatic)) was performed, and the arithmetic mean roughness Ra displayed in the measurement results was recorded. The average value of the arithmetic mean roughness Ra obtained for the 10 samples was calculated as the arithmetic mean roughness Ra (μm) of the fiber surface of the liquid crystal polymer fiber.

[0096] In addition, the standard deviation was calculated from the data of the arithmetic mean roughness Ra of the 10 samples, and the variation coefficient of the arithmetic mean roughness Ra was calculated using the following formula. Coefficient of variation of arithmetic mean roughness Ra = standard deviation / average value

[0097] (Amount of layered silicate mineral attached) The amount of layered silicate mineral attached to the liquid crystal polymer fiber was measured by the Soxhlet extraction method. Specifically, 5 g of liquid crystal polymer fiber to which a dispersion containing layered silicate mineral and oil was applied was placed in a Soxhlet extractor, and the extraction solvent n-hexane and zeolite were placed in a flat-bottom flask, and extraction was performed for 2.5 hours in a 10 L water bath (100 °C). After that, n-hexane was evaporated, the weight of the oil after extraction was weighed, and the oil adhesion rate was calculated by a gravimetric method from the weight of the liquid crystal polymer fiber before extraction. The amount of layered silicate mineral attached to the fiber was calculated from the obtained oil adhesion rate and the ratio of the oil and layered silicate mineral in the dispersion. The obtained amount of layered silicate mineral attached was divided by the surface area of ​​the fiber to obtain the amount attached per unit surface area (μg / cm 2 The surface area of ​​the fiber was calculated by assuming that the fiber surface was flat and without irregularities and that the fiber cross section was a perfect circle, converting the single fiber fineness measured as described below into a single fiber diameter, calculating the surface area of ​​the single fiber, and multiplying this by the number of filaments.

[0098] (Total fineness, single fiber fineness) Based on JIS L 1013:2010 8.3.1 A method, a 10m reel of liquid crystal polymer fiber was taken using a measuring device "Wrap Reel by Motor Driven" manufactured by Daiei Scientific Instruments Co., Ltd., and the weight (g) was multiplied by 1000 and measured three times per level, and the average of the three measurements was taken as the total fineness (dtex) of the obtained liquid crystal polymer fiber. The quotient obtained by dividing this value by the number of filaments was taken as the single fiber fineness (dtex).

[0099] (Wear resistance) Using a high-speed yarn frictional adhesion tester "TM-200" manufactured by Daiei Kagaku Seiki Seisakusho Co., Ltd., the liquid crystal polymer fiber to be tested was brought into contact with a friction body (sapphire) at an angle of 120°, a load of 0.4 g / dtex was applied to the fiber, and the fiber was reciprocated at a stroke length of 3 cm and a speed of 95 times / min. The presence or absence of fuzz was confirmed every 100 reciprocations by magnifying the image 20 times with a camera. The number of times that fuzz generation was confirmed was taken as the measured value, and the test was performed 5 times, and the average number (times) was calculated. Here, it was determined that fuzz generation occurred when fuzz with a length of 1 mm or more was confirmed.

[0100] [Example 1] Smectite with a median diameter of 18 μm and an interlayer distance of 1.2 nm was added to an aqueous solution of spinning oil to a content of 1.07 wt%, and stirred for 12 hours at a peripheral speed of 15 m / s using a high-dispersion homogenizer. The resulting dispersion had a viscosity of 7.2 mPa s, was thixotropic, and had excellent dispersion state retention.

[0101] Chips (granular molded bodies) of molten anisotropic aromatic polyester (α) (Mp0: 278 ° C.) composed of 73 / 27 (mol%) of structural units derived from 4-hydroxybenzoic acid and structural units derived from 6-hydroxy-2-naphthoic acid were dried with hot air at 120 ° C. for 4 hours or more. Then, melt extrusion was performed with a single-screw extruder, and the molten mixture was supplied to the spinning head while being metered with a gear pump. In the spinning head, the molten mixture was filtered with a metal nonwoven filter, and the molten mixture was discharged at a discharge rate of 135.4 g / min from a spinneret with a hole diameter of 0.10 mm φ, a land length of 0.14 mm, and 300 holes. The above-mentioned dispersion liquid was applied to the extruded filamentous material through an oiling guide arranged directly below the spinneret, and the material was taken up by the first godet roll, passed through the second godet roll, and then passed through a dancer roller and wound into a cheese shape at 800 m / min by a winder to obtain a spun raw yarn of 1670 dtex / 300 filaments.

[0102] The obtained raw spun yarn was unwound in the longitudinal direction (perpendicular to the fiber circumferential direction) using a rewinder and rewound around a stainless steel bobbin with holes wrapped with nonwoven fabric to obtain a bobbin package for heat treatment. The obtained package was heat-treated at 275°C for 16 hours in a nitrogen atmosphere to obtain a heat-treated yarn of melt-anisotropic aromatic polyester fiber. The heat-treated yarn was then unwound in the transverse direction (horizontal to the fiber circumferential direction) using a rewinder and rewound, during which a finishing oil was applied. The analysis results of the obtained melt-anisotropic aromatic polyester fiber are shown in Table 5.

[0103] [Example 2] Instead of the melt anisotropic aromatic polyester (α) described in Example 1, a melt anisotropic aromatic polyester (β) (Mp0: 309 ° C.) consisting of 60 / 20 / 15 / 5 (mol%) of 6-hydroxy-2-naphthoic acid-derived structural units, 2,6-naphthalenedicarboxylic acid-derived structural units, hydroquinone-derived structural units, and 4,4'-dihydroxybiphenyl-derived structural units was used, and a spinneret with a hole diameter of 0.06 mmφ, a land length of 0.084 mm, and 100 holes was used, and the discharge amount during spinning was 10.13 g / min, and the winding speed was 900 m / min. The same procedure as in Example 1 was used to obtain a spun raw yarn. Thereafter, a heat-treated yarn was obtained in the same manner as in Example 1, except that the heat treatment temperature of the spun raw yarn was 295 ° C.

[0104] [Example 3] A heat-treated yarn was obtained in the same manner as in Example 1, except that a spinneret with a hole diameter of 0.06 mmφ, a land length of 0.084 mm, and 100 holes was used, the output rate during spinning was 11.25 g / min, and the winding speed was 1000 m / min.

[0105] [Example 4] A dispersion was obtained in the same manner as in Example 1, except that the stirring time was changed to 30 minutes. The viscosity of the obtained dispersion was 6.2 mPa s, it had thixotropy, and it was possible to maintain the dispersed state. A heat-treated yarn was obtained in the same manner as in Example 1, except that the above dispersion was used.

[0106] [Comparative Example 1] Mica with a median diameter of 2 μm and an interlayer distance of 0.9 nm was added to an aqueous solution of spinning oil to a content of 1.07 wt%, and stirred for 12 hours at a peripheral speed of 1.2 m / s using a low-dispersion propeller blade stirrer. The viscosity of the resulting dispersion was 5.5 mPa·s and it had thixotropy, but the dispersed state could not be maintained. A heat-treated yarn was obtained in the same manner as in Example 1, except that the above dispersion was used.

[0107] [Comparative Example 2] Mica with a median diameter of 2 μm and an interlayer distance of 0.9 nm was added to an aqueous solution of spinning oil to a content of 1.07 wt%, and the mixture was stirred for 12 hours at a peripheral speed of 15 m / s using a high-dispersion homogenizer. The viscosity of the resulting dispersion was 5.7 mPa·s and it had thixotropy, but the dispersed state could not be maintained. A heat-treated yarn was obtained in the same manner as in Example 1, except that the above dispersion was used.

[0108] [Comparative Example 3] Smectite with a median diameter of 18 μm and an interlayer distance of 1.2 nm was added to an aqueous solution of spinning oil to a content of 1.07 wt%, and stirred for 12 hours at a peripheral speed of 1.2 m / s using a low-dispersion propeller blade stirrer. The viscosity of the resulting dispersion was 5.8 mPa·s and it had thixotropy, but the dispersed state could not be maintained. A heat-treated yarn was obtained in the same manner as in Example 1, except that the above dispersion was used.

[0109] [Comparative Example 4] A dispersion was obtained in the same manner as in Comparative Example 3, except that the stirring time with the low-dispersion propeller blade stirrer was changed to 24 hours. The viscosity of the obtained dispersion was 5.8 mPa s and it had thixotropy, but the dispersed state could not be maintained. A heat-treated yarn was obtained in the same manner as in Example 1, except that the above dispersion was used.

[0110] [Comparative Example 5] A heat-treated yarn was obtained in the same manner as in Example 1, except that the rotation speed of the gear pump connected to the oiling guide arranged immediately below the spinneret was adjusted to change the amount of the dispersion liquid applied. The amount of smectite attached to the heat-treated yarn was 2.00 μg / cm 2 It was.

[0111] [Comparative Example 6] A heat-treated yarn was obtained in the same manner as in Example 3, except that the rotation speed of the gear pump connected to the oiling guide arranged immediately below the spinneret was adjusted to change the amount of the dispersion liquid applied. The amount of smectite attached to the heat-treated yarn was 1.30 μg / cm 2 It was.

[0112] [Comparative Example 7] A heat-treated yarn was obtained in the same manner as in Example 1, except that the layered silicate mineral was not added and an aqueous solution of spinning oil was used.

[0113] [Comparative Example 8] A heat-treated yarn was obtained in the same manner as in Example 2, except that the rotation speed of the gear pump connected to the oiling guide arranged immediately below the spinneret was adjusted to change the amount of the dispersion liquid applied. The amount of smectite attached to the heat-treated yarn was 1.30 μg / cm 2 It was.

[0114] [Table 5]

[0115] As shown in Table 5, the arithmetic mean roughness Ra of the fiber surface of the liquid crystal polymer fibers of Examples 1 to 4 is within a specific range, and shows excellent abrasion resistance. Abrasion resistance is affected by the type of liquid crystal polymer constituting the fiber and the fiber configuration such as the single fiber fineness and the number of filaments, but the liquid crystal polymer fibers of Examples 1 and 4 have excellent abrasion resistance compared to the liquid crystal polymer fibers of Comparative Examples 1 to 4 and 7, which have similar types of liquid crystal polymer and fiber configurations, and which have small arithmetic mean roughness Ra of the fiber surface, and the liquid crystal polymer fiber of Comparative Example 5, which has a large arithmetic mean roughness Ra of the fiber surface.

[0116] The liquid crystal polymer fiber of Example 2 has superior abrasion resistance compared to the liquid crystal polymer fiber of Comparative Example 8, which has the same type of liquid crystal polymer and fiber structure, but has a large arithmetic mean roughness Ra of the fiber surface.

[0117] The liquid crystal polymer fiber of Example 3 has superior abrasion resistance compared to the liquid crystal polymer fiber of Comparative Example 6, which has the same type of liquid crystal polymer and fiber structure, but has a large arithmetic mean roughness Ra of the fiber surface. [Industrial Applicability]

[0118] Liquid crystal polymer fibers can be used for a variety of applications, including general industrial materials, civil engineering and construction materials, various reinforcing materials, electrical and electronic component materials, and various textile products.

[0119] As described above, the preferred embodiments of the present invention have been described. However, various additions, modifications, and omissions can be made without departing from the spirit of the present invention, and such additions, modifications, and omissions are also included within the scope of the present invention.

Claims

1. A liquid crystal polymer fiber having an arithmetic mean roughness Ra of the fiber surface of 0.20 to 0.50 μm.

2. 2. The liquid crystal polymer fiber according to claim 1, wherein the coefficient of variation of the arithmetic mean roughness Ra of the fiber surface is 0.45 or less.

3. 3. The liquid crystal polymer fiber according to claim 1, comprising a liquid crystal polymer containing at least one structural unit selected from the group consisting of structural units represented by the following formulas (I) to (III): -O-Ar １ -CO- (I) -CO-Ar ２ -CO- (II) _________________ ３ ____) (In the formula, Ar １ is a phenylene group, a naphthylene group, or a biphenylylene group, and Ar ２ and Ar ３ are each independently a phenylene group, a naphthylene group, a biphenylylene group, a diphenyletherdiyl group, a diphenylmethyldiyl group, or a diphenylsulfondiyl group, and Ar １ , Ar ２ and Ar ３ Each hydrogen atom in the aromatic ring may be independently substituted with a halogen atom, an alkyl group, an alkoxy group, an aryl group, an aralkyl group, an aryloxy group, or an aralkyloxy group, and each of X and Y is independently an oxygen atom or a secondary amino group (—NH—).

4. 3. The liquid crystal polymer fiber according to claim 1, wherein at least one layered silicate mineral selected from the group consisting of smectite, vermiculite, and chlorite is attached to the surface of the fiber.

5. 3. The liquid crystal polymer fiber according to claim 1, wherein a layered silicate mineral having an interlayer distance of 1.0 nm or more is attached to the fiber surface.

6. 5. The liquid crystal polymer fiber according to claim 4, wherein the layered silicate mineral has an adhesion amount per unit surface area of ​​0.20 to 1.20 μg / cm ２ Liquid crystal polymer fiber.

7. A fiber structure comprising at least a portion of the liquid crystal polymer fiber according to claim 1 or 2.

8. a step of stirring an aqueous oil solution containing a layered silicate mineral having an interlayer distance of 1.0 nm or more with a stirrer at a peripheral speed of 6 m / s or more to prepare a dispersion having a viscosity of 6.0 mPa s or more; The amount of the layered silicate mineral attached per unit surface area on the fiber surface is 0.20 to 1.20 μg / cm ２ and applying the dispersion to the liquid crystal polymer fibers so that the dispersion becomes

9. 9. The method for producing a liquid crystal polymer fiber according to claim 8, wherein after the step of applying the dispersion, the liquid crystal polymer fiber is subjected to a heat treatment and / or a heat drawing.

10. 10. The method for producing liquid crystal polymer fibers according to claim 8, wherein the aqueous oil agent solution contains 0.1 to 10 wt % of the layered silicate mineral.

11. 10. The method for producing liquid crystal polymer fibers according to claim 8, wherein the stirring time in the dispersion preparation step is 30 minutes or more.