Metal-coated liquid crystal polyester multifilament and method for manufacturing the same

Abstract

The objective is to provide a metal-coated liquid crystal polyester multifilament that improves the adhesion between the coated metal and the multifilament during bending, reduces the slack of single fibers during twisting of the multifilament, prevents the metal coating from peeling off, and results in high-grade processed products with good quality. [Solution] A metal-coated liquid crystal polyester multifilament characterized by having a metal layer surrounding the single fibers of a multifilament made of liquid crystal polyester, wherein the arithmetic mean roughness of the surface of the metal layer is 0.25 μm or less.

Description

Technical Field

[0001] The present invention relates to a metal-coated liquid crystal polyester multifilament.

Background Art

[0002] Conventionally, metal wires have been used as electric wires and electromagnetic shielding materials. In recent years, research and development of conductive fiber materials in which metal is coated on multifilaments has been promoted for weight reduction and space saving. Particularly, as multifilaments with high strength, metal-coated multifilaments such as liquid crystal polyester multifilaments coated with metal have been studied. Many of these metal-coated multifilaments have been proposed by applying a plating treatment on the fiber surface to coat the metal (for example, Patent Documents 1 and 2). According to these, not only can weight reduction and diameter reduction be achieved, but also the flexibility of the multifilament can be utilized to achieve flexural resistance.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, metal-coated multifilaments with the above plating process have a problem in that the plating tends to peel off when repeatedly bent, so it is necessary to improve the adhesion between the coated metal and the multifilament. Generally, to adhere plating to nonmetals, adhesion is achieved by the anchoring effect of the plating on the surface irregularities of the nonmetal. However, if the surface irregularities are significant, the stress applied during bending tends to concentrate in one area, making it easier for the plating to peel off. In addition, when metal-coated multifilaments are processed into electrical wires or electromagnetic shielding materials, it is common to twist them to improve their passability through the process. However, if the surface of the coated metal multifilament is irregular, single fiber slack is likely to occur during twisting, and these slack areas become defects during processing, tending to worsen the quality of the processed product. Therefore, it is necessary to suppress surface irregularities.

[0005] Patent Document 1 improves the adhesion between the coating metal and the multifilament by suppressing plating cracking on high-strength fibers by setting the plating thickness within a certain range relative to the outer diameter of the fiber. Patent Document 2 defines the amount of Pd catalyst in the liquid crystal polyester and allows the coating metal to penetrate not only the fiber surface but also the inside of the fiber, thereby making it less likely for the plating to peel off and achieving good adhesion between the coating metal and the multifilament when bending.

[0006] Patent documents 1 and 2 both describe how increasing the amount of plating relative to a certain fiber diameter suppresses plating peeling during bending and achieves good adhesion between the coated metal and the multifilament. However, they do not mention anything about the smoothness of the plated surface, and the influence of surface smoothness on adhesion during bending is not considered. Furthermore, there is no description or suggestion of the problem that the aforementioned single-fiber slack may occur due to surface smoothness. In other words, it cannot be said that the prior art documents recognized the problem of single-fiber slack that specifically occurs when liquid crystal polyester multifilaments are processed to a higher order, and no specific disclosure of methods for suppressing it was made. As a result, it was difficult to obtain a metal-coated liquid crystal polyester multifilament that suppresses single-fiber slack and also has good adhesion of the metal coating during bending.

[0007] Therefore, the objective is to provide a metal-coated liquid crystal polyester multifilament that solves the problems of the conventional technology described above, improves the adhesion between the coated metal and the multifilament when bent, reduces the slack of single fibers when the multifilament is twisted, prevents the metal coating from peeling off easily, and results in high-grade processed products with good quality. [Means for solving the problem]

[0008] To solve the above problems, the present invention has the following configuration. That is, the metal-coated liquid crystal polyester multifilament according to the present invention is characterized in that it has a metal layer made of metal around a single fiber of a multifilament made of liquid crystal polyester, and the arithmetic mean roughness of the surface of the metal layer is 0.25 μm or less.

[0009] In the metal-coated liquid crystal polyester multifilament of the present invention, it is preferable that the arithmetic mean roughness of the multifilament made of liquid crystal polyester is 0.01 μm or more and 0.15 μm or less, the metal layer is formed by plating, and the metal contains at least one selected from the group consisting of copper, gold, silver, iron, zinc, tin, and nickel.

[0010] In the metal-coated liquid crystal polyester multifilament of the present invention, it is preferable that the tensile strength of the multifilament made of the liquid crystal polyester is 15 cN / dtex or more.

[0011] In the metal-coated liquid crystal polyester multifilament of the present invention, it is preferable that the amount of metal contained in the multifilament made of liquid crystal polyester is 15 ppm or less by mass per million.

[0012] In the metal-coated liquid crystal polyester multifilament of the present invention, it is preferable that the liquid crystal polyester consists of structural units (I), (II), (III), (IV), and (V) shown in the following chemical formulas.

[0013] [ka]

[0014] In the above-described metal-coated liquid crystal polyester multifilament, it is preferable that the proportion of structural unit (I) is 40 mol% or more and 85 mol% or less relative to the total of structural units (I), (II), and (III), the proportion of structural unit (II) is 60 mol% or more and 90 mol% or less relative to the total of structural units (II) and (III), and the proportion of structural unit (IV) is 40 mol% or more and 95 mol% or less relative to the total of structural units (IV) and (V).

[0015] Furthermore, the method for manufacturing metal-coated liquid crystal polyester multifilaments according to the present invention is characterized by plating a metal around single fibers of a multifilament made of liquid crystal polyester having an arithmetic mean surface roughness of 0.01 μm or more and 0.15 μm or less.

[0016] In a method for manufacturing metal-coated liquid crystal polyester multifilaments, it is preferable that the single fiber diameter of the multifilament made of liquid crystal polyester is 15 μm or more and 40 μm or less, and that the number of filaments of the multifilament made of liquid crystal polyester is 30 or more and 250 or less. [Effects of the Invention]

[0017] The metal-coated liquid crystal polyester multifilament of the present invention has improved adhesion of the coating metal to the fibers and reduced slack in the single fibers during twisting, making it suitable for use in electric wires and electromagnetic shielding materials. [Modes for carrying out the invention]

[0018] The metal-coated liquid crystal polyester multifilament and its manufacturing method according to the present invention will be described in detail below.

[0019] The method for manufacturing the metal-coated liquid crystal polyester multifilament is not limited in any way, as long as the metal-coated liquid crystal polyester multifilament specified in the present invention can be obtained, but preferred embodiments are described below.

[0020] The liquid crystal polyester used in the present invention refers to a polyester that exhibits optical anisotropy (liquid crystallinity) when heated and melted. This can be identified by placing a sample made of liquid crystal polyester on a hot stage, heating it with temperature increase under a nitrogen atmosphere, and observing the presence or absence of transmitted light of the sample with a polarized microscope.

[0021] Examples of the liquid crystal polyester include a polymer (a) of an aromatic oxycarboxylic acid, a polymer (b) of an aromatic dicarboxylic acid and an aromatic diol, an aliphatic diol, a copolymer (c) of the above (a) and the above (b), etc. Among them, a polymer composed only of aromatics is preferred. A polymer composed only of aromatics exhibits excellent strength and elastic modulus when made into fibers. Also, a conventionally known method can be used for the polymerization formulation of the liquid crystal polyester.

[0022] Here, examples of the aromatic oxycarboxylic acid include hydroxybenzoic acid (such as p-hydroxybenzoic acid), hydroxynaphthoic acid, etc. (such as 6-hydroxy-2-naphthoic acid), or their alkyl, alkoxy, halogen-substituted products, etc.

[0023] Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, diphenyldicarboxylic acid, naphthalenedicarboxylic acid, diphenyl ether dicarboxylic acid, diphenoxyethane dicarboxylic acid, diphenyl ethane dicarboxylic acid, etc., or their alkyl, alkoxy, halogen-substituted products, etc.

[0024] Furthermore, examples of the aromatic diol include hydroquinone, resorcinol, dihydroxybiphenyl, naphthalenediol, etc., or their alkyl, alkoxy, halogen-substituted products, etc., and examples of the aliphatic diol include ethylene glycol, propylene glycol, butanediol, neopentyl glycol, etc.

[0025] In addition to the monomers mentioned above, liquid crystal polyesters can be copolymerized with other monomers to the extent that their liquid crystal properties are not impaired. Examples include aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and dodecanedionic acid; alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid; polyethers such as polyethylene glycol; polysiloxanes; aromatic iminocarboxylic acids; aromatic diimines; and aromatic hydroxyimines.

[0026] Preferred examples of liquid crystal polyesters polymerized from the monomers mentioned above include liquid crystal polyester copolymerized from p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, liquid crystal polyester copolymerized from p-hydroxybenzoic acid, 4,4'-dihydroxybiphenyl, isophthalic acid and / or terephthalic acid, and liquid crystal polyester copolymerized from p-hydroxybenzoic acid, 4,4'-dihydroxybiphenyl, isophthalic acid, terephthalic acid and hydroquinone.

[0027] In particular, a liquid crystal polyester consisting of structural units (I), (II), (III), (IV), and (V) shown in the following chemical formulas is preferred. In this invention, a structural unit refers to a unit that can constitute a repeating structure in the main chain of a polymer.

[0028] [ka]

[0029] This combination results in molecular chains possessing appropriate crystallinity and nonlinearity, i.e., a melting point that allows for melt spinning. Consequently, the spinnable material exhibits good spinnability at spinning temperatures set between the polymer's melting point and thermal decomposition temperature, yielding relatively uniform fibers in the longitudinal direction and possessing appropriate crystallinity, thereby increasing the fiber's strength and modulus of elasticity.

[0030] Furthermore, it is preferable to combine components consisting of diols that are not bulky, such as structural units (II) and (III), and have high linearity. By combining these components, the molecular chains in the fiber adopt an ordered, less disordered structure, while crystallinity is not excessively increased and interactions perpendicular to the fiber axis can be maintained. As a result, in addition to high strength and elastic modulus, excellent abrasion resistance can also be obtained.

[0031] The structural unit (I) described above is preferably 40 to 85 mol%, more preferably 65 to 80 mol%, and even more preferably 68 to 75 mol%, relative to the total of structural units (I), (II), and (III). By setting it within this range, the crystallinity can be set to an appropriate range, resulting in high strength and elastic modulus, and the melting point is also within a range that allows for melt spinning.

[0032] The amount of structural unit (II) is preferably 60 to 90 mol%, more preferably 60 to 80 mol%, and even more preferably 65 to 75 mol%, relative to the total of structural units (II) and (III). By keeping the amount within this range, crystallinity is not excessively increased, and interactions perpendicular to the fiber axis are maintained, thereby improving wear resistance.

[0033] The amount of structural unit (IV) is preferably 40 to 95 mol%, more preferably 50 to 90 mol%, and even more preferably 60 to 85 mol%, relative to the total of structural units (IV) and (V). By setting the amount within this range, the melting point of the polymer is within an appropriate range, resulting in good spinnability at a spinning temperature set between the melting point and the thermal decomposition temperature of the polymer, and obtaining fibers with fine single fiber fineness and relatively uniformity in the longitudinal direction.

[0034] Furthermore, it is preferable that the sum of structural units (II) and (III) and the sum of (IV) and (V) are substantially equimolar. Substantially equimolar here means that equimolar amounts of dioxy units and dicarbonyl units constituting the main chain are present, and that the terminal structural units do not necessarily have to be equimolar, as one or the other may be unevenly distributed.

[0035] The particularly preferred ranges for each structural unit of liquid crystal polyester are as follows. The preferred range for each structural unit is defined as the range when the sum of structural units (I), (II), (III), (IV), and (V) is 100 mol%. Liquid crystal polyester fibers can be suitably obtained by adjusting the composition within this range to satisfy the above-mentioned conditions. Structural unit (I) 45-65 mol% Structural unit (II) 12-18 mol% Structural unit (III) 3-10 mol% Structural unit (IV) 5-20 mol% Structural unit (V) 2-15 mol%

[0036] The weight-average molecular weight (Mw) of the liquid crystal polyester, in terms of polystyrene equivalent, is preferably 30,000 or more, and more preferably 50,000 or more. A Mw of 30,000 or more allows for appropriate viscosity at spinning temperatures, improving spinnability, and higher Mw results in higher strength, elongation, and modulus of elasticity of the resulting fibers. Furthermore, from the viewpoint of achieving excellent fluidity, an Mw of less than 250,000 is preferred, and less than 150,000 is more preferred. In this invention, Mw refers to the value obtained by the method described in the examples.

[0037] The melting point of the liquid crystal polyester is preferably in the range of 200 to 380°C, more preferably 250 to 350°C, and even more preferably 290 to 340°C, from the viewpoint of ease of melt spinning and heat resistance. In this invention, the melting point refers to the value obtained by the method described in the examples.

[0038] Furthermore, other polymers can be added to or used in combination with the liquid crystal polyester, as long as the effects of the present invention are not impaired. Addition and combination refer to mixing polymers with each other, or partially or entirely mixing other polymers with one or more components in a composite spinning process involving two or more components. Examples of other polymers that may be added include polyester, vinyl polymers such as polyolefins and polystyrene, polycarbonate, polyamide, polyimide, polyphenylene sulfide, polyphenylene oxide, polysulfone, aromatic polyketone, aliphatic polyketone, semi-aromatic polyesteramide, polyetheretherketone, and fluororesin. Suitable examples include polyphenylene sulfide, polyetheretherketone, nylon 6, nylon 66, nylon 46, nylon 6T, nylon 9T, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycyclohexanedimethanol terephthalate, and polyester 99M. When these polymers are added or used in combination, it is preferable that their melting point be within ±30°C of the liquid crystal polyester's melting point to avoid impairing spinnability. Furthermore, to improve the strength and elastic modulus of the resulting fibers, the amount added or used in combination is preferably 50% by weight or less relative to the liquid crystal polyester, more preferably 5% by weight or less, and most preferably not to add or use any other polymers at all.

[0039] The liquid crystal polyester may contain small amounts of additives such as inorganic substances like kaolin and silica, colorants, matting agents, flame retardants, antioxidants, ultraviolet absorbers, infrared absorbers, crystal nucleating agents, fluorescent whitening agents, end group encapsulants, and compatibilizers, as long as they do not impair the effects of the present invention.

[0040] The single fiber diameter of the liquid crystal polyester multifilament obtained by melt spinning the liquid crystal polyester is preferably 15 μm or more, more preferably 18 μm or more, even more preferably 20 μm or more, preferably 40 μm or less, and more preferably 35 μm or less. When the single fiber diameter of the liquid crystal polyester multifilament is above the lower limit above, it is easier to obtain the strength required for higher-grade processed products. Furthermore, when the single fiber diameter of the liquid crystal polyester multifilament is below the upper limit above, uniform cooling to the inside of the single fiber becomes possible after extrusion, resulting in stable spinnability and making it easier to obtain liquid crystal polyester multifilament with good fluff quality. In addition, the fiber surface area exposed to the outside air during heat treatment increases, which is advantageous for high strength and high elasticity. The single fiber diameter refers to the value obtained by the method described in the examples.

[0041] The number of single fibers (filaments) in liquid crystal polyester multifilaments is preferably 30 to 250, more preferably 30 to 240, and even more preferably 30 to 220. By setting the number of single fibers to 30 to 250, the productivity of the multifilaments can be improved, and the increased surface area of ​​the fibers exposed to the outside air during heat treatment promotes the solid-phase polymerization reaction, reducing variations in strength and resulting in liquid crystal polyester multifilaments with uniform physical properties. Furthermore, there is no problem in separating or combining the samples obtained by spinning to produce liquid crystal polyester multifilaments with a number of single fibers of 30 to 250. Note that the number of single fibers refers to the value obtained by the method described in the examples.

[0042] The total fineness of the liquid crystal polyester multifilament is preferably 50 to 1000 dtex, more preferably 50 to 900 dtex, and even more preferably 50 to 800 dtex. A fineness of 50 to 1000 dtex provides high process passability and is suitable for applications such as electric wires and electromagnetic shielding materials where weight reduction is required. Furthermore, samples obtained by spinning can be separated or combined to produce liquid crystal polyester multifilament with a total fineness of 50 to 1000 dtex. Note that the total fineness refers to the value obtained by the method described in the examples.

[0043] In liquid crystal polyester multifilaments, it is preferable to perform solid-phase polymerization after melt spinning to form filaments.

[0044] The arithmetic mean roughness of the surface of the liquid crystal polyester multifilament is preferably 0.01 μm or more and 0.15 μm or less. The arithmetic mean roughness referred to here is a value calculated based on JIS B 0601:2013. Since the surface roughness of the liquid crystal polyester multifilament is reflected in the surface roughness of the metal-coated liquid crystal polyester multifilament, if the arithmetic mean roughness of the surface of the liquid crystal polyester multifilament is 0.15 μm or less, it becomes easier to make the surface arithmetic mean roughness of the metal-coated liquid crystal polyester multifilament 0.25 μm or less. On the other hand, if it is 0.01 μm or less, an anchoring effect cannot be obtained when metal coating is applied, resulting in poor adhesion.

[0045] To achieve an arithmetic mean roughness of 0.15 μm or less for liquid crystal polyester multifilaments, for example, damage to the fibers and fibrillation can be minimized during the manufacturing process. Specifically, in the rewinding process from the spinning package, it is preferable to set the rewinding speed to 550 m / min or less and the amount of oil added to 2.0% by weight or more. By rewinding at a low speed and with a high amount of oil as described above, damage to the fibers and fibrillation can be suppressed, and the arithmetic mean roughness of the liquid crystal polyester multifilaments can be controlled to 0.15 μm or less.

[0046] The arithmetic mean roughness of the liquid crystal polyester multifilament is determined by the value measured before the metal coating is applied, as described later. While it is common to remove the metal coating by either physical polishing or chemicals, both methods damage the surface of the liquid crystal polyester multifilament, making it impossible to restore the original surface roughness. Therefore, the value measured before the metal coating is used as the arithmetic mean roughness of the liquid crystal polyester multifilament.

[0047] Liquid crystal polyester multifilaments are preferably subjected to solid-phase polymerization. Solid-phase polymerization allows for obtaining the strength required for electric wires.

[0048] The strength of the liquid crystal polyester multifilament is preferably 15 cN / dtex or higher. Preferably, it is 15.0 cN / dtex or higher, more preferably 17.0 cN / dtex or higher, and even more preferably 19.0 cN / dtex or higher. A strength of 15.0 cN / dtex or higher makes it suitable for electric wires where high strength and lightweight are required. While there is no particular upper limit to the strength, a achievable upper limit is approximately 30.0 cN / dtex. In this invention, strength refers to the breaking strength measured by the strength-to-elongation test described in the examples.

[0049] The metal content of the liquid crystal polyester multifilament is preferably 15 ppm or less, more preferably 12 ppm or less, and even more preferably 10 ppm or less. The strength referred to in this invention is the value obtained by the method described in the examples. A metal content of 15 ppm or less does not affect the resistance value when used as a metal-coated liquid crystal polyester multifilament, and good performance can be obtained when used as an electrical wire or electromagnetic shielding material. A lower metal content is preferable, and none is most preferable.

[0050] The metal-coated liquid crystal polyester multifilament of the present invention is characterized by a metal coating around the single fibers constituting the liquid crystal polyester multifilament. The metal is not particularly limited, but preferably includes at least one selected from the group consisting of copper, gold, silver, iron, zinc, tin, and nickel, more preferably includes at least one selected from the group consisting of copper, iron, zinc, tin, and nickel, and even more preferably includes at least one selected from the group consisting of copper, iron, zinc, and tin. Including these metals makes it easier to improve the conductivity and flexural fatigue resistance of the metal-coated liquid crystal polyester multifilament. These metals can be used individually or as alloys of two or more types.

[0051] The method for coating the single fibers constituting the liquid crystal polyester multifilament with metal is not particularly limited, but a metal plating treatment that suppresses surface roughness is preferred. The metal plating treatment may be carried out by known methods, such as vapor deposition, sputtering, electroplating, electroless plating, or supercritical plating. These plating methods may be combined; for example, electroless plating or supercritical plating may be performed followed by electroplating. Among these, electroless plating is preferred.

[0052] The thickness of the metal coating surrounding the single fibers of the liquid crystal polyester multifilament is 0.05 to 20.0 μm, and more preferably 0.1 to 15.0 μm.

[0053] The arithmetic mean roughness of the metal-coated liquid crystal polyester multifilament surface must be 0.25 μm or less. The arithmetic mean roughness is measured using the same method as the method used to measure the arithmetic mean roughness of the liquid crystal polyester multifilament. If the arithmetic mean roughness of the metal-coated liquid crystal polyester multifilament surface exceeds the above upper limit, the difference in the unevenness of the metal coating becomes too large, and the stress applied during bending concentrates, making the metal coating prone to peeling. Furthermore, since metal-coated liquid crystal polyester multifilament is more rigid than ordinary multifilament, slack in single fibers during higher-order processing can be suppressed by twisting under high tension. However, if the difference in the unevenness of the metal coating is large, gaps are likely to form between single fibers even when twisted under high tension, causing slack in the single fibers. This results in unevenness when the coating is applied for wire production, degrading the quality. Therefore, it is necessary to reduce the difference in the unevenness of the metal coating. To achieve an arithmetic mean roughness of 0.25 μm or less on the surface of the metal-coated liquid crystal polyester multifilament, the arithmetic mean roughness of the liquid crystal polyester multifilament can be set to 0.15 μm or less.

[0054] It is desirable to twist the metal-coated liquid crystal polyester multifilament before higher-level processing. Twisting improves the uniformity of strength and the passability through the process. There are no particular restrictions on the twisting method, and it can be carried out using conventional techniques, and the twisting direction can be either S or Z. A twist count of 50 t / m to 250 t / m is preferable. A twist count of 50 t / m or more improves the alignment of the single fibers, while a twist count of 250 t / m or less prevents the twisted metal-coated liquid crystal polyester multifilament itself from twisting.

[0055] The resulting metal-coated liquid crystal polyester multifilament exhibits improved adhesion of the coating metal to the liquid crystal polyester multifilament and reduced slack in the single fibers during twisting, resulting in a high-quality processed product with less peeling of the metal coating. Metal-coated liquid crystal polyester multifilament can be suitably used in electric wires and electromagnetic shielding materials that are coated with insulating resin, and is particularly suitable for use in automotive harness wires that are routed through gaps in automobile parts. [Examples]

[0056] Next, the embodiments will be described in detail, but the present invention is not limited thereto. The definitions of the properties used in the main text of the specification and the embodiments, as well as the measurement and calculation methods for each physical property, are shown below.

[0057] (1) Melting point In differential calorimetry performed with a differential scanning calorimeter (TA Instruments DSC2920), the endothermic peak temperature (T) observed when measuring under a temperature increase condition of 50°C to 20°C / min is... m1 After the observation of ), approximately T m1 The endothermic peak temperature (T) observed when the temperature is held at +20°C for 5 minutes, then cooled to 50°C at a rate of 20°C / min, and then measured again under the heating condition of 20°C / min is measured. m2 The melting point was defined as ). The same procedure was performed twice, and the average of the two results was used to determine the melting point T of the liquid crystal polyester. m2 (°C)

[0058] (2) Weight-average molecular weight (molecular weight) on a polystyrene basis A mixed solvent of pentafluorophenol / chloroform = 35 / 65 (by weight) was used as the solvent, and the liquid crystal polyester was dissolved in the mixed solvent while stirring at 120°C for 20 minutes. At this time, the liquid crystal polyester was prepared to a concentration of 0.04% by weight and used as the sample for GPC measurement. This was measured using a Waters GPC analyzer, and the Mw was determined in terms of polystyrene equivalent. The same procedure was performed twice, and the average of the two results was taken as the weight-average molecular weight (Mw). Column: ShodexK-G(1) Shodex K-806M(2) Shodex K-802(1) Detector: Differential refractive index detector RI (Type 2414) Temperature: 23±2℃ Flow rate: 0.8mL / min Injection volume: 0.200mL.

[0059] (3) Single fiber diameter The single fiber diameter (μm) was calculated by dividing the total fineness by the fiber density and the number of single fibers to obtain the cross-sectional area of ​​a single fiber.

[0060] (4) Total fineness The total fineness (dtex) was determined by measuring the positive fineness at a specified load of 0.045 cN / dtex according to JIS L 1013(2010)8.3.1 Method A.

[0061] (5) Number of filaments The calculation was performed using the method specified in JIS L 1013(2010)8.4.

[0062] (6) Strength Measurements were taken under the constant-speed elongation conditions specified in JIS L 1013 (2010) 8.5.1 Standard Time Test. The sample was tested using Orientec's "TENSILON" UCT-100, with a gripping distance (measurement length) of 250 mm and a tensile speed of 50 mm / min. Strength was defined as the stress at fracture.

[0063] (7) Metal content After heating and ashing the liquid crystal polyester multifilament, it was thermally decomposed with sulfuric acid and nitric acid, and then dissolved in dilute nitric acid to a fixed volume. The metal content in this solution was measured by ICP emission spectroscopy using a sequential ICP emission spectrometer (e.g., SII Nanotechnology Co., Ltd. "SPS4000").

[0064] (8) Arithmetic mean roughness The samples were placed in a straight line on a table, and 3D imaging was performed using a non-contact 3D roughness meter (AMETEK "Nexview NX2") with a 1 mm square field of view. For the single fibers in the captured images, the arithmetic mean roughness in the longitudinal direction was calculated according to JIS B 0601 (2013). Five arbitrary points were measured in the longitudinal direction, and the average value was taken as the arithmetic mean roughness for liquid crystal polyester multifilament and metal-coated liquid crystal polyester multifilament.

[0065] (9) Adhesion of the metal coating Based on the peel test method of JIS H 8504 (1999), using Nichiban Co., Ltd.'s cellophane tape (registered trademark), samples with no peeling of the metal coating were considered good, samples with peeling were considered bad, and samples with no peeling were considered acceptable.

[0066] (10) Irregularities after insulating resin coating A metal-coated liquid crystal polyester multifilament was coated with an insulating resin, and the number of irregularities on the resin coating per 100m was evaluated using an outer diameter irregularity detector (TM-1100XY, manufactured by Takikawa Engineering Co., Ltd.). Irregularities were defined as areas with a deviation of ±0.02mm from the smooth surface of the resin coating. 0 to 3 irregularities were considered particularly good, 4 to 9 were good, and 10 or more were poor. A sample with 9 or fewer irregularities on the coating was considered acceptable.

[0067] [Example 1] In a 5 L reaction vessel equipped with a stirring blade and distillation tube, 870 parts by weight of p-hydroxybenzoic acid, 327 parts by weight of 4,4'-dihydroxybiphenyl, 157 parts by weight of isophthalic acid, 292 parts by weight of terephthalic acid, 89 parts by weight of hydroquinone, and 1433 parts by weight of acetic anhydride (1.08 equivalents of the total phenolic hydroxyl groups) were charged. Under a nitrogen gas atmosphere, the temperature was raised from room temperature to 145°C in 30 minutes while stirring, and the reaction was carried out at 145°C for 2 hours. After that, the temperature was raised to 330°C in 4 hours. The polymerization temperature was maintained at 330°C, and the pressure was reduced to 1.0 mmHg (133 Pa) in 1.5 hours. The reaction was continued for another 20 minutes, and the polycondensation was completed when the predetermined torque was reached. Next, the volume inside the reaction vessel was reduced to 1.0 kg / cm³. 2 The polymer was pressurized to 0.1 MPa and extruded into strands through a nozzle with a single circular discharge port of 10 mm in diameter, and then pelletized by a cutter.

[0068] This liquid crystal polyester consists of 54 mol% p-hydroxybenzoic acid units, 16 mol% 4,4'-dihydroxybiphenyl units, 8 mol% isophthalic acid units, 15 mol% terephthalic acid units, and 7 mol% hydroquinone units. Its melting point is 315°C, and its melt viscosity, measured using a high-efficiency flow tester at 330°C and a shear rate of 1,000 / sec, was 30 Pa·sec. Its Mw was 145,000.

[0069] Using this liquid crystal polyester, water and oligomers were removed by vacuum drying at 120°C for 12 hours. The moisture content of the liquid crystal polyester at this time was 50 ppm. This dried liquid crystal polyester was melt-extruded using a single-screw extruder (heater temperature 290-340°C), and the polymer was supplied to the spinning pack while being weighed with a gear pump. The spinning temperature from the extruder outlet to the spinning pack at this time was 335°C. In the spinning pack, the polymer was filtered using a metal nonwoven fabric filter with a filtration accuracy of 15 μm, and the polymer was extruded at a discharge rate of 65 g / min (0.90 g / min per hole) from a nozzle with 72 holes with a pore size of 0.13 mm and a land length of 0.26 mm.

[0070] Immediately after extrusion, the liquid crystal polyester multifilaments were cooled and solidified at room temperature. An oiling roller was used to coat the filaments with a solution of talc dispersed at 1% by weight in water (oil agent), and all 72 filaments were picked up at a speed of 1000 m / min using a Nelson roller. The amount of oil agent applied at this time was 3.0% by weight. The multifilaments picked up by the Nelson roller were then wound into a cheese shape using a wing traverse type winder via a dancer arm. A spun yarn of liquid crystal polyester multifilament with a total fineness of 660 dtex and a single fiber diameter of 29 μm was obtained.

[0071] The fibers were unwound from this spinning package in the longitudinal direction (perpendicular to the fiber's circumferential direction) and rewound at a constant speed of 400 m / min using a winding machine (SSP-WV8P type precision winder manufactured by Kozu Seisakusho Co., Ltd.). A stainless steel bobbin was used as the core material for rewinding, with a tension of 0.005 cN / dtex and a winding density of 0.50 g / cm². 3 That's what I decided.

[0072] The obtained rolled-up samples were subjected to solid-phase polymerization in a sealed oven under the following conditions: heating from room temperature to 240°C, holding at 240°C for 3 hours, then heating to 290°C, and holding at 290°C for 20 hours. During solid-phase polymerization, dehumidified nitrogen was supplied at a flow rate of 100 L / min, and the air was exhausted through the exhaust port to prevent the oven from becoming pressurized.

[0073] The resulting solid-phase polymerization package was then attached to a feeder that could be rotated by an inverter motor, and the fibers were unfurled while being fed out laterally (in the direction of fiber circulation) at 200 m / min, and then wound onto a product package using a winding machine.

[0074] The physical properties of the resulting liquid crystal polyester multifilament are shown in Table 1.

[0075] [Table 1]

[0076] Metal-coated polyester multifilaments were obtained by applying a catalyst, electroless plating, and electroplating to liquid crystal polyester multifilaments as described below.

[0077] A palladium nucleus catalyst was applied to the liquid crystal polyester as a pretreatment to a thickness of approximately 50 nm and activated. A copper plating layer with a thickness of 0.5 μm was formed in contact with the catalyst by electroless copper plating. The plating solution used was an aqueous solution with the following composition. EDTA-4Na is ethylenediaminetetraacetic acid tetrasodium. Copper sulfate 15g / L Formalin 3g / L EDTA-4Na 35g / L Sodium hydroxide 5g / L Stabilizer (small amount) A small amount of lubricant

[0078] A copper plating layer with a thickness of 4.0 μm was formed by electroplating in contact with the copper plating layer. The plating solution used was an aqueous solution with the following composition. Copper sulfate 200g / L Sulfuric acid 50g / L

[0079] The physical properties of the resulting metal-coated liquid crystal polyester multifilament are shown in Table 1.

[0080] Metal-coated liquid crystal polyester multifilaments were twisted in an S-twist configuration at a twist count of 120 t / m, and then coated with molten insulating resin and water-coated. The number of surface irregularities on the resulting resin-coated metal-coated liquid crystal polyester multifilaments is shown in Table 1.

[0081] [Example 2] A metal-coated liquid crystal polyester multifilament was obtained in the same manner as in Example 1, except that the amount of oil applied was set to 2.5% by weight.

[0082] [Example 3] A metal-coated liquid crystal polyester multifilament was obtained in the same manner as in Example 1, except that the yarn was rewound from the spinning package at a rate of 500 m / min using a winding machine.

[0083] [Example 4] Metal-coated liquid crystal polyester multifilaments were obtained in the same manner as in Example 1, except that the total fineness of the liquid crystal polyester multifilaments was 430 dtex and the single fiber diameter was 23 μm.

[0084] [Example 5] A metal-coated liquid crystal polyester multifilament was obtained in the same manner as in Example 1, except that a liquid crystal polyester resin (melting point 280°C) consisting of 73 mol% p-hydroxybenzoic acid units and 27 mol% 6-hydroxy-2-naphthoic acid units was used as the liquid crystal polyester resin, and the solid-phase polymerization temperature was set to 260°C and the solid-phase polymerization time to 10 hours.

[0085] [Comparative Example 1] A metal-coated liquid crystal polyester multifilament was obtained in the same manner as in Example 1, except that the amount of oil applied was 1.5% by weight.

[0086] [Comparative Example 2] A metal-coated liquid crystal polyester multifilament was obtained in the same manner as in Example 1, except that the yarn was rewound from the spinning package at a rate of 600 m / min using a winding machine. Table 1 shows the fiber properties of Comparative Examples 1 and 2. [Industrial applicability]

[0087] The metal-coated liquid crystal polyester multifilament of the present invention can be suitably used in electric wires and electromagnetic shielding materials that are coated with insulating resin, and among these, it can be suitably used in automotive harness wires that are routed through gaps in automobile parts.

Claims

1. A metal-coated liquid crystal polyester multifilament characterized by having a metal layer surrounding a single fiber of a multifilament made of liquid crystal polyester, wherein the arithmetic mean roughness of the surface of the metal layer is 0.25 μm or less.

2. The metal-coated liquid crystal polyester multifilament according to claim 1, wherein the arithmetic mean roughness of the surface of the multifilament made of liquid crystal polyester is 0.01 μm or more and 0.15 μm or less, the metal layer is formed by plating, and the metal comprises at least one selected from the group consisting of copper, gold, silver, iron, zinc, tin, and nickel.

3. The metal-coated liquid crystal polyester multifilament according to claim 1 or 2, wherein the tensile strength of the multifilament made of liquid crystal polyester is 15 cN / dtex or more.

4. The metal-coated liquid crystal polyester multifilament according to claim 1 or 2, wherein the part per million mass of the metal content in the multifilament made of liquid crystal polyester is 15 ppm or less.

5. The metal-coated liquid crystal polyester multifilament according to claim 1 or 2, wherein the liquid crystal polyester comprises structural units (I), (II), (III), (IV), and (V) shown in the following chemical formulas. 【Chemistry 1】

6. The metal-coated liquid crystal polyester multifilament according to claim 5, wherein the proportion of structural unit (I) is 40 mol% or more and 85 mol% or less relative to the total of structural units (I), (II), and (III), the proportion of structural unit (II) is 60 mol% or more and 90 mol% or less relative to the total of structural units (II) and (III), and the proportion of structural unit (IV) is 40 mol% or more and 95 mol% or less relative to the total of structural units (IV) and (V).

7. A method for manufacturing metal-coated liquid crystal polyester multifilaments, characterized by arranging a metal around the single fibers of a multifilament made of liquid crystal polyester having an arithmetic mean surface roughness of 0.01 μm or more and 0.15 μm or less by plating.

8. The method for manufacturing a metal-coated liquid crystal polyester multifilament according to claim 7, wherein the single fiber diameter of the multifilament made of liquid crystal polyester is 15 μm or more and 40 μm or less, and the number of filaments of the multifilament made of liquid crystal polyester is 30 or more and 250 or less.

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