Metal-coated liquid crystal polyester multifilament

Abstract

A metal-covered liquid crystal polyester multifilament that contains two or more metal-covered liquid crystal polyester monofilaments, each of which is obtained by covering the surface of a liquid crystal polyester monofilament with a metal that has a thickness of from 0.1 to 20 μm, wherein the ratio of the number of conglutinated fibers that are conglutinated metal-covered liquid crystal polyester monofilaments to the total number of fibers is 75% or less in a cross-sectional photograph thereof obtained by means of X-ray CT.

Description

[Technical Field]

[0001] The present invention relates to a metal-coated liquid crystal polyester multifilament that can be used as a conductive member in the field of smart textiles, electromagnetic wave shielding applications, and the like. [Background technology]

[0002] In recent years, smart textiles that combine clothing and devices have been actively developed (see, for example, Patent Document 1). For example, known smart textiles include clothing made with conductive fibers that measures information such as heart rate in real time when worn, and knit heaters that have electrical circuits directly knitted into the clothing and are heated by external electrodes. The conductive fibers used in such smart textiles are required to have not only electrical conductivity and strength, but also resistance to bending fatigue and wearability.

[0003] On the other hand, plated fibers in which high-strength fibers such as polyarylate fibers are coated with metal have been studied as conductive fibers with high conductivity and strength (for example, Patent Document 2). In order to impart strength and elastic modulus to such polyarylate fibers, they are usually used by subjecting spun raw yarns to solid-state polymerization through heat treatment. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-9259 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-195091 Summary of the Invention [Problem to be solved by the invention]

[0005] However, according to the investigations of the present inventors, it was found that metal-coated fibers plated with polyarylate fibers as described in Reference 2 do not have sufficient resistance to bending fatigue, and resistance can increase significantly when repeatedly bent. In addition, due to low flexibility (or softness), the wearability of clothing when used as a smart textile material is insufficient.

[0006] Therefore, an object of the present invention is to provide a metal-coated liquid crystalline polyester multifilament that is excellent in wearability and resistance to flex fatigue when used as a smart textile material. [Means for solving the problem]

[0007] As a result of extensive research to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by a metal-coated liquid crystal polyester multifilament comprising two or more metal-coated liquid crystal polyester monofilaments, each having a surface coated with a 0.1 to 20 μm thick metal, when the ratio of the number of glued fibers to the total number of fibers is 75% or less, and have completed the present invention. That is, the present invention includes the following aspects.

[0008] [1] A metal-coated liquid crystal polyester multifilament comprising two or more metal-coated liquid crystal polyester monofilaments each having a 0.1 to 20 μm thick metal coating on the surface of a liquid crystal polyester monofilament, wherein in a cross-sectional photograph measured by X-ray CT, the ratio of the number of aggregated fibers to which the metal-coated liquid crystal polyester monofilaments are aggregated is 75% or less of the total number of fibers. [2] The metal-coated liquid crystal polyester multifilament according to [1], wherein in a cross-sectional photograph measured by X-ray CT, the distance between any two points furthest apart on the metal surface covering the adhesive fiber is 11 times or less the diameter of the metal-coated liquid crystal polyester monofilament. [3] The metal-coated liquid crystal polyester multifilament according to [1] or [2], which has a tensile strength of 16 cN / dtex or more. [4] The metal-coated liquid crystal polyester multifilament according to any one of [1] to [3], wherein the metal comprises at least one selected from the group consisting of copper, silver, gold, iron, zinc, lead, palladium, nickel, chromium, tin, titanium, aluminum, indium, and vanadium. [5] The metal-coated liquid crystal polyester multifilament according to any one of [1] to [4], wherein the liquid crystal polyester monofilament has a fineness of 11 dtex or more. [6] The metal-coated liquid crystal polyester multifilament according to any one of [1] to [5], wherein the specific resistance, which is the ratio of the resistance after a flexural fatigue test to the resistance before the flexural fatigue test, is 25 or less. [Effects of the Invention]

[0009] The metal-coated liquid crystalline polyester multifilament of the present invention is excellent in wearability and resistance to bending fatigue when used as a smart textile material. [Brief explanation of the drawings]

[0010] [Figure 1] This is an X-ray CT cross-sectional photograph showing that the metal (white part) cannot penetrate between the monofilaments because the fibers are stuck together. [Figure 2] This is an X-ray CT cross-sectional photograph showing the state in which the monofilament is partially coated with metal. [Figure 3] This is an X-ray CT cross-sectional photograph showing that the entire monofilament is covered with metal. [Figure 4] This is an X-ray CT cross-sectional photograph showing a metal-coated fiber in which the entire monofilament is coated with metal, and the metal is in close contact with itself. [Figure 5] 1 is an X-ray CT cross-sectional photograph of the metal-coated liquid crystal polyester multifilament obtained in Example 4. Since the adhered fibers and the non-aggregated fibers are mixed, it is used to explain the adhered fibers. [Figure 6]FIG. 6 is a diagram showing some of the aggregated fibers and non-aggregated fibers with numbers in the X-ray cross-sectional photograph of the metal-coated liquid crystal polyester multifilament shown in FIG. 5. [Figure 7] FIG. 6 is a diagram showing the distance between any two points on the metal surface covering the adhered fibers in the most distant adhered fibers in the X-ray CT cross-sectional photograph of FIG. 5. [Figure 8] 1 is an X-ray CT cross-sectional photograph of the metal-coated liquid crystal polyester multifilament obtained in Example 1, showing that the fibers are not easily agglutinated and the metal has penetrated deep into the fibers. [Figure 9] 1 is an X-ray CT cross-sectional photograph of the metal-coated liquid crystal polyester multifilament obtained in Comparative Example 3, showing a state in which the fibers are significantly stuck together and the metal does not penetrate between the monofilaments. [Figure 10] FIG. 1 is a diagram showing longitudinal lengths a and a' and transverse lengths b and b' for determining yarn hardness. DETAILED DESCRIPTION OF THE INVENTION

[0011] The metal-coated liquid crystal polyester multifilament of the present invention comprises two or more metal-coated liquid crystal polyester monofilaments each having a 0.1 to 20 μm thick metal coating on the surface of a liquid crystal polyester monofilament, and in a cross-sectional photograph measured by X-ray CT, the proportion of the number of agglutinated fibers to which the metal-coated liquid crystal polyester monofilaments are agglutinated (sometimes referred to as agglutination rate) is 75% or less relative to the total number of fibers.

[0012] In light of the fact that conventional liquid crystal polyester multifilaments are prone to forming stuck portions due to heat treatment during solid-state polymerization, making it difficult to form a metal coating in these portions, the inventors succeeded in reducing the stuck portions, i.e., reducing the proportion of stuck fibers to 75% or less of the total number of fibers.Unexpectedly, they found that the resulting metal-coated fibers had significantly improved flexibility (or softness) as well as resistance to bending fatigue, and that the fibers also had excellent wearability when used as smart textile materials. In this specification, "filament" may be referred to as "fiber," "monofilament" as "single fiber," "coated" as "plated," "liquid crystal polyester multifilament" simply as "multifilament," and "liquid crystal polyester monofilament" simply as "monofilament," and "liquid crystal polyester multifilament" and "liquid crystal polyester monofilament" may be collectively referred to as "liquid crystal polyester fiber."

[0013] <Liquid Crystal Polyester Monofilament> High-strength liquid crystal polyester fibers can be produced, for example, by melt-spinning liquid crystal polyester and then solid-phase polymerizing the resulting spun yarn. Liquid crystal polyester multifilament is a fiber consisting of two or more liquid crystal polyester monofilaments. Liquid crystal polyesters are polyesters that exhibit optical anisotropy (liquid crystallinity) in the molten phase, and can be identified by, for example, placing a sample on a hot stage, heating it under a nitrogen atmosphere, and observing the transmitted light through the sample with a polarizing microscope. Liquid crystal polyesters are composed of repeating structural units derived from, for example, aromatic diols, aromatic dicarboxylic acids, or aromatic hydroxycarboxylic acids, and the chemical structure of these structural units is not particularly limited as long as it does not impair the effects of the present invention. Furthermore, liquid crystal polyesters may also contain structural units derived from aromatic diamines, aromatic hydroxyamines, or aromatic aminocarboxylic acids, provided that the effects of the present invention are not impaired.

[0014] For example, preferred structural units include those shown in Table 1. [Table 1]

[0015] Here, Y is present in a number ranging from 1 to the maximum number that can be substituted on the aromatic ring, and each Y is independently selected from the group consisting of 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 [benzyl group (phenylmethyl group), phenethyl group (phenylethyl group), etc.], an aryloxy group (e.g., a phenoxy group, etc.), and an aralkyloxy group (e.g., a benzyloxy group, etc.).

[0016] More preferred structural units include the structural units described in Examples (1) to (18) shown in the following 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 structural units that constitute the polymer.

[0017] [Table 2]

[0018] [Table 3]

[0019] [Table 4]

[0020] In the structural units of Tables 2, 3, and 4, n is an integer of 1 or 2, and each of the structural units n=1 and n=2 may exist alone or in combination; Y1 and Y2 may each independently represent 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, or a t-butyl group), 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), an aralkyloxy group (e.g., a benzyloxy group), etc. Among these, preferred Ys include a hydrogen atom, a chlorine atom, a bromine atom, or a methyl group.

[0021] Furthermore, examples of Z include substituents represented by the following formulas. [ka]

[0022] A preferred liquid crystalline polyester preferably has two or more types of naphthalene skeletons as a structural unit. Particularly preferably, the liquid crystalline polyester contains both a structural unit (A) derived from hydroxybenzoic acid and a structural unit (B) derived from hydroxynaphthoic acid. For example, the structural unit (A) may be represented by the following formula (A), and the structural unit (B) may be represented by the following formula (B). From the viewpoint of easily improving melt moldability, the ratio of the structural unit (A) to the structural unit (B) may be preferably in the range of 9 / 1 to 1 / 1, more preferably 7 / 1 to 1 / 1, and even more preferably 5 / 1 to 1 / 1.

[0023] [ka] [ka]

[0024] The total of the structural units (A) and the structural units (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 the total structural units. Liquid crystal polyesters in which the structural units (B) account for 4 to 45 mol % of the polymer are particularly preferred.

[0025] The melting point of the liquid crystal polyester preferably used in the present invention is preferably 250 to 360°C, more preferably 260 to 320°C. Here, the melting point refers to the main absorption peak temperature observed when measured using a differential scanning calorimeter (DSC; Mettler "TA3000") according to JIS K7121. Specifically, 10 to 20 mg of sample is placed in an aluminum pan and sealed in the DSC apparatus. Nitrogen is passed through the sample as a carrier gas at 100 cc / min, and the endothermic peak is measured when the temperature is increased at 20°C / min. If a clear peak does not appear in the first run of DSC measurement due to the type of polymer, it is recommended to increase the temperature to 50°C higher than the expected flow temperature at a heating rate of 50°C / min, hold the temperature at that temperature for 3 minutes, completely melt the polymer, and then cool it to 50°C at a cooling rate of -80°C / min. The endothermic peak is then measured at a heating rate of 20°C / min.

[0026] The liquid crystal polyester may contain thermoplastic polymers such as polyethylene terephthalate, modified polyethylene terephthalate, polyolefin, polycarbonate, polyamide, polyphenylene sulfide, polyether ether ketone, and fluororesin, as long as the effects of the present invention are not impaired. Furthermore, various additives may be added, such as inorganic substances such as titanium oxide, kaolin, silica, and barium oxide, colorants such as carbon black, dyes, and pigments, antioxidants, ultraviolet absorbers, and light stabilizers.

[0027] In the liquid crystal polyester fiber obtained by melt spinning the liquid crystal polyester, the fineness of the liquid crystal polyester monofilament is preferably 1.5 dtex or more, more preferably 2.5 dtex or more, and even more preferably 5.0 dtex or more. In a preferred embodiment of the present invention, the fineness of the liquid crystal polyester monofilament is preferably 11 dtex or more, more preferably 15 dtex or more, even more preferably 20 dtex or more, and particularly preferably 25 dtex or more. When the fineness of the liquid crystal polyester monofilament is equal to or greater than the above-mentioned lower limit, it is easy to suppress the agglutination of single fibers due to solid-state polymerization, and it is easy to improve the wearability and flex fatigue resistance. Furthermore, the upper limit of the fineness of the liquid crystal polyester monofilament is preferably 100 dtex or less, more preferably 50 dtex or less. When the fineness of the liquid crystal polyester monofilament is equal to or less than the above-mentioned upper limit, it is easy to increase the solidification efficiency immediately after melt spinning and the solid-state polymerization rate.

[0028] <Metal> The metal-coated liquid crystal polyester multifilament of the present invention is a liquid crystal polyester monofilament having a surface coated with a metal having a thickness of 0.1 to 20 μm. In this specification, the metal includes not only the metals described later, but also conductive metal oxides and metal nitrides using the metals described later.

[0029] The metal is not particularly limited, but preferably contains at least one selected from the group consisting of copper, silver, gold, iron, zinc, lead, palladium, nickel, chromium, tin, titanium, aluminum, indium, and vanadium, and more preferably contains at least one selected from the group consisting of copper, nickel, silver, gold, and iron. The inclusion of these metals tends to improve the electrical conductivity and flex fatigue resistance of the metal-coated liquid crystal polyester multifilament. These metals can be used alone or in combination.

[0030] The thickness of the metal coating on the surface of the liquid crystal polyester monofilament is 0.1 to 20 μm, preferably 0.2 μm or more, more preferably 0.5 μm or more, and even more preferably 15 μm or less, more preferably 10 μm or less. If the metal thickness is above the lower limit, the conductivity increases and the initial resistance value is easily reduced, while if it is below the upper limit, the wearability and flex fatigue resistance are easily improved. The metal thickness can be measured by X-ray CT, for example, by the method described in the Examples.

[0031] <Metal-coated liquid crystal polyester multifilament> The metal-coated liquid crystal polyester multifilament of the present invention comprises two or more metal-coated liquid crystal polyester monofilaments in which the surface of the liquid crystal polyester monofilament is coated with the metal.

[0032] In the metal-coated liquid crystal polyester multifilament of the present invention, in a cross-sectional photograph measured by X-ray CT, the ratio of the number of glued fibers (glug ratio) of the metal-coated liquid crystal polyester monofilament to the total number of fibers is 75% or less, so that it has high flexibility (or softness) and excellent wearability when used as a smart textile material. Furthermore, since the glued portions are reduced, it also has excellent resistance to bending fatigue, and changes in resistance value can be effectively suppressed even when repeatedly bent. As such, the metal-coated liquid crystal polyester multifilament of the present invention can achieve both excellent wearability and bending fatigue resistance, and is therefore useful as a smart textile material (e.g., electrodes and wiring of smart textiles). Furthermore, because it has excellent bending fatigue resistance, it can also be suitably used in electric wires, electromagnetic wave shielding materials, etc.

[0033] The proportion of the number of glued fibers (glue ratio) relative to the total number of fibers is preferably 70% or less, more preferably 65% or less, even more preferably 50% or less, even more preferably 40% or less, particularly preferably 30% or less, even more particularly preferably 20% or less, and most preferably 15% or less. When the glue ratio is below the above upper limit, it is easier to further improve softness and wearability, and to further increase bending fatigue resistance. The lower limit of the glue ratio is usually 0% or more.

[0034] The adhesion rate can be calculated using the following formula by taking 10 cross-sectional photographs of the metal-coated liquid crystal polyester multifilament at 50 μm intervals (intervals perpendicular to the cross section) using X-ray CT, counting the number of adhered fibers in each of the 10 cross-sectional photographs and the number of fibers in the entire cross-sectional photograph. Adhesion rate (%) = (number of adhesed fibers) / (total number of fibers) x 100

[0035] In the present invention, the X-ray CT cross-sectional photograph is a cross-sectional photograph in which 90% or more of the filaments are visible when the number of filaments in the metal-coated liquid crystalline polyester multifilament is 100 or less, and in which at least 100 filaments are visible when the number of filaments is more than 100.

[0036] Distinguishing between stuck and unstuck fibers can be achieved by the following method. For example, FIG. 5 is an X-ray CT cross-sectional photograph of the metal-coated liquid crystal polyester multifilament obtained in Example 4. In the X-ray CT photograph (image), the plated metal coating the fiber is observed as a white color. Therefore, based on the shape of the metal portion (white portion), it is possible to distinguish between stuck and unstuck monofilaments. Specifically, the state of unstuck fibers is shown in FIGS. 3 and 4, and the state of stuck fibers is shown in FIGS. 1 and 2.

[0037] The X-ray CT cross-sectional photograph in Figure 3 shows that the entire periphery (entire surface) of the monofilament is covered with metal, and it can be determined that the fiber is not stuck together. The X-ray CT cross-sectional photograph in Figure 4 shows the state in which the metal-coated monofilaments shown in Figure 3 are in close contact with each other, and since the monofilaments themselves are not stuck together, it can be determined that they are not stuck together.

[0038] The X-ray CT cross-sectional photograph in Figure 1 shows that metal has been plated on the outer periphery of the multiple monofilament bundles that have stuck together, and the metal has not penetrated between the monofilaments, which indicates that the fibers are stuck together. The X-ray CT cross-sectional photograph in Figure 2 shows a state in which some parts are not coated with metal. This indicates that a load has been applied to the metal-plated adhered fibers on the outer periphery as shown in Figure 1, causing the adhered fibers to separate (or break down), and it can be determined that the fibers are adhered.

[0039] Here, the glued fibers will be described in more detail with reference to Fig. 6. Fig. 6 is a diagram showing some of the glued fibers and unagglutinated fibers by numbers in an X-ray cross-sectional photograph of the metal-coated liquid crystal polyester multifilament shown in Fig. 5.

[0040] Non-sticky fibers include, for example, a monofilament whose entire peripheral edge (entire surface) is coated with metal (the entire, approximately circular outer periphery of the monofilament is white with no gaps), as shown in (1) of Figure 6, and a non-sticky monofilament such as that shown in (1) that is in close contact with other fibers, as shown in (2) of Figure 6 (the former corresponds to the state in Figure 3, and the latter corresponds to the state in Figure 4). The agglutinated fibers (aggregated fibers) are fibers other than the non-aggregated fibers, such as those shown in Figure 6 (3) where the peripheral edge of the monofilament is not partially coated with metal (where the approximately circular outer periphery of the monofilament is not partially white), and those shown in Figure 6 (4) and (5) where the non-metal coated portions of the metal-coated monofilament as shown in Figure 6 (3) (the gaps where the approximately circular outer periphery of the monofilament is not white) are at least connected (the former corresponds to the state in Figure 2, and the latter corresponds to the state in Figure 1).

[0041] As described above, in this specification, agglutinated fiber means a fiber in which the peripheral portion (surface portion) of the monofilament is not partially metal-plated in an X-ray cross-sectional photograph, or a fiber that includes a portion in which multiple monofilaments are directly connected or in contact without being interposed by a coating metal.

[0042] In addition, in the formula for the agglutination rate, the number of agglutinated fibers in the X-ray CT cross-sectional photograph refers to the total number of monofilaments constituting all agglutinated fibers. Regarding the number of agglutinated fibers, for example, the agglutinated fiber shown in Figure 6 (4) is composed of 22 monofilaments, so the number of agglutinated fibers is 22, and the agglutinated fiber shown in Figure 6 (5) is composed of 5 monofilaments, so the number of agglutinated fibers is 5. The number of agglutinated fibers in the X-ray CT cross-sectional photograph can be calculated by counting and adding up the number of monofilaments constituting each agglutinated fiber included in the X-ray CT cross-sectional photograph. Furthermore, the total number of fibers refers to the total number of monofilaments in the X-ray CT cross-sectional photograph, including both agglutinated and unglutinated fibers. Note that monofilaments present at the edge of the X-ray CT cross-sectional photograph and partially hidden from view are not included in the number of agglutinated fibers and the total number of fibers.

[0043] In the cross-sectional photographs measured by X-ray CT, the distance between any two points farthest apart on the metal surface covering the agglutination fiber is referred to as the agglutination distance. The agglutination distance indicates the width of the agglutination fiber containing the widest part among the agglutination fibers in the 10 X-ray CT cross-sectional photographs. Therefore, it can be said that the shorter the agglutination distance, the smaller the size of the agglutination fiber contained in the metal-coated liquid crystalline polyester multifilament. More specifically, the adhesion distance can be obtained by selecting the agglutination fiber with the greatest distance between any two points on the metal surface (white area) covering the agglutination fiber and measuring the distance between those two points. For example, in the X-ray CT cross-sectional photograph of the metal-coated liquid crystal polyester multifilament in Figure 6, the agglutination fiber with the greatest distance between any two points on the metal surface covering the agglutination fiber is the agglutination fiber shown in (4). Therefore, the agglutination fiber shown in (4) is selected, and the adhesion distance can be obtained by measuring the distance between those two points as shown in Figure 7.

[0044] In one embodiment of the present invention, in the metal-coated liquid crystalline polyester multifilament of the present invention, the adhesion distance is preferably 11 times or less the diameter of the metal-coated liquid crystalline polyester monofilament. Therefore, it is easy to improve softness and wearability, and to increase flex fatigue resistance. The adhesion distance is more preferably 9 times or less, even more preferably 7 times or less, and particularly preferably 5 times or less. When the adhesion distance is equal to or less than the above upper limit, it is easy to further improve softness and wearability, and to further increase flex fatigue resistance. The lower limit of the adhesion distance is usually 1.2 times or more. When the diameters of the plurality of metal-coated liquid crystal polyester monofilaments are different, the sticking distance can be calculated based on the largest diameter.

[0045] In this specification, flexural fatigue resistance refers to the property of resistance values that do not change even when a metal-coated liquid crystalline polyester multifilament is repeatedly bent. This can be evaluated, for example, by the specific resistance value, which is the ratio of the resistance value after a flexural fatigue test to the resistance value before the test. The specific resistance value can be measured by the following method. First, the initial resistance value of the metal-coated liquid crystalline polyester multifilament is measured using a resistance measuring device. Next, the metal-coated liquid crystalline polyester multifilament is bent using a flexural fatigue tester under the following conditions: a bending angle of 120°, a bending speed of 60 rpm, a load of 100 g, and 5,000 flexes. If the specific resistance at 5,000 flexes is close to 1 and comparison is difficult, the metal-coated liquid crystalline polyester multifilament is plated with a metal such as nickel, and the resistance value is measured again and then substituted into the following formula to calculate the specific resistance value. For example, the resistance value may be calculated using the method described in the examples. Resistivity value = (resistivity value after flexural fatigue test) / (initial resistance value before flexural fatigue test)

[0046] In one embodiment of the present invention, the resistivity of the metal-coated liquid crystalline polyester multifilament after 5,000 flexures is preferably 25 or less, more preferably 20 or less, even more preferably 15 or less, even more preferably 10 or less, particularly preferably 7 or less, and even more particularly preferably 5 or less. When the resistivity is equal to or less than the above upper limit, excellent flex fatigue resistance and high conductivity after flexure are likely to be exhibited. Furthermore, in one embodiment of the present invention, the initial resistance of the metal-coated liquid crystalline polyester multifilament is preferably 0.01 to 10 Ω / 10 cm, more preferably 0.1 to 5 Ω / 10 cm, and even more preferably 0.2 to 3 Ω / 10 cm. When the initial resistance is within the above range, conductivity is likely to be increased.

[0047] In this specification, wearability refers to the ease of putting on clothing using the metal-coated liquid crystal polyester multifilament of the present invention as a smart textile material, and the ease of movement or comfort after putting it on.The wearability improves as the flexibility (or softness) of the metal-coated liquid crystal polyester multifilament increases, and therefore can be evaluated by measuring the flexibility (or softness), for example, by yarn hardness (also called yarn displacement).

[0048] In one embodiment of the present invention, the yarn hardness (yarn displacement) of the metal-coated liquid crystalline polyester multifilament is preferably 25 m·dtex·μm or more, more preferably 30 m·dtex·μm or more, even more preferably 35 m·dtex·μm or more, even more preferably 40 m·dtex·μm or more, particularly preferably 50 m·dtex·μm or more, and even more particularly preferably 60 m·dtex·μm or more, and preferably 100 m·dtex·μm or less. When the yarn hardness is at least the above lower limit, the flexibility is high and wearability is easily improved. On the other hand, when the yarn hardness is at most the above upper limit, the fiber strength is easily increased. The yarn hardness can be measured by the loop method, for example, by the method described in the Examples.

[0049] The tensile strength of the metal-coated liquid crystalline polyester multifilament is preferably 16 cN / dtex or more, more preferably 18 cN / dtex or more, and even more preferably 21 cN / dtex or more. When the tensile strength is above the lower limit, the mechanical strength is easily increased. The upper limit of the tensile strength of the metal-coated liquid crystalline polyester multifilament is preferably 35 cN / dtex or less, more preferably 30 cN / dtex or less. When the tensile strength is below the upper limit, flexibility is easily maintained while maintaining flexural fatigue resistance and tensile strength. The tensile strength can be measured using a benchtop precision universal testing machine, for example, by the method described in the Examples. Note that the tensile strength of the multifilament after plating is dominated by the tensile strength of the multifilament before plating, so the tensile strength of the metal-coated liquid crystalline polyester multifilament may be a value measured using a liquid crystalline polyester multifilament before plating.

[0050] The total fineness of the liquid crystal polyester multifilaments in the metal-coated liquid crystal polyester multifilament is not particularly limited, but is preferably 10 dtex or more, more preferably 50 dtex or more, even more preferably 100 dtex or more, particularly preferably 200 dtex or more, and is preferably 10,000 dtex or less, more preferably 5,000 dtex or less, even more preferably 3,000 dtex or less, particularly preferably 2,000 dtex or less. The number of metal-coated liquid crystal polyester monofilaments in the metal-coated liquid crystal polyester multifilament is preferably 3 or more, more preferably 5 or more, and preferably 1,000 or less, more preferably 500 or less. When the total fineness of the liquid crystal polyester multifilaments and the number of metal-coated liquid crystal polyester monofilaments in the metal-coated liquid crystal polyester multifilament are within the above ranges, it is easy to improve wearability, flex fatigue resistance, light weight, and strength.

[0051] The metal-coated liquid crystal polyester multifilament may be untwisted or loosely twisted, and from the viewpoint of stabilizing the resistance value, loosely twisted is preferred. Furthermore, the metal-coated liquid crystal polyester multifilament may be subjected to an opening treatment and / or smoothing treatment. For example, by producing a woven fabric using such a multifilament that has been opened and / or smoothed, the woven fabric can be made thin.

[0052] The form of the metal-coated liquid crystal polyester multifilament is not particularly limited, and may be, for example, UD (Unidirectional), nonwoven fabric, woven fabric, knitted fabric, braided cord, or mixed yarn.

[0053] <Metal-coated Liquid Crystalline Polyester Multifilament Manufacturing Method> The method for producing the metal-coated liquid crystalline polyester multifilament of the present invention is not particularly limited, but may include, for example, the following steps: (i) a spinning step of melt-spinning the liquid crystalline polyester; (ii) a solid-state polymerization step of solid-state polymerizing the raw spinning yarn by heat treatment to obtain a liquid crystalline polyester multifilament; (iii) A plating process for coating the liquid crystal polyester multifilament with metal A method comprising the steps of:

[0054] In the step (i), the liquid crystal polyester can be melt-spun by a conventional method, usually at a temperature 10 to 50° C. higher than the melting point of the liquid crystal polyester.

[0055] In step (ii), the raw spun yarn spun in step (i) is heat-treated to undergo solid-state polymerization. The heat treatment during solid-state polymerization improves strength and modulus. In a preferred embodiment of the present invention, by setting the heat treatment temperature lower than conventional temperatures, it is possible to suppress sticking of the raw spun yarn and reduce the sticking rate and sticking distance, thereby improving wearability and flex fatigue resistance. The heat treatment temperature is preferably 295°C or lower, more preferably 290°C or lower, even more preferably 280°C or lower, even more preferably 270°C or lower, and particularly preferably 260°C or lower. When the heat treatment temperature is below the above upper limit, the sticking rate and sticking distance are likely to be reduced, and wearability and flex fatigue resistance are likely to be improved. Furthermore, the heat treatment temperature is preferably 200°C or higher, more preferably 220°C or higher, and even more preferably 240°C or higher. When the heat treatment temperature is above the above lower limit, solid-state polymerization is likely to proceed, and fiber strength and modulus are likely to be increased. In one embodiment of the present invention, the heat treatment may be carried out under temperature conditions in which the temperature is gradually increased from a temperature not higher than the melting point of the liquid crystal polyester fiber within the above-mentioned heat treatment temperature range.

[0056] The heat treatment time can be appropriately selected depending on the heat treatment temperature and is preferably 30 minutes to 30 hours, more preferably 2 to 20 hours, and even more preferably 4 to 18 hours. When the heat treatment time is within the above range, although it depends on the heat treatment temperature, solid-state polymerization also easily proceeds, making it easy to reduce the sticking rate and sticking distance, and easy to improve wearability and flex fatigue resistance.

[0057] The method for adjusting the conglutination rate and conglutination distance of the metal-coated liquid crystal polyester multifilament of the present invention to fall within the above-described ranges is not particularly limited. For example, the conglutination rate and conglutination distance can be adjusted to fall within the ranges of the present invention by appropriately adjusting the heat treatment temperature, heat treatment time, and polyester monofilament fineness in step (ii), preferably within the above-described ranges. For example, the conglutination rate and conglutination distance tend to decrease as the fineness of the liquid crystal polyester monofilament increases, and the conglutination rate and conglutination distance tend to decrease as the heat treatment temperature decreases. Furthermore, optimizing the heat treatment temperature, heat treatment time, and polyester monofilament fineness in combination makes it easier to further reduce the conglutination rate and conglutination distance. In particular, appropriately adjusting the heat treatment temperature and / or heat treatment time in combination with the polyester monofilament fineness makes it easier to further reduce the conglutination rate and conglutination distance. Alkali treatment may be performed within a range that does not impair the effects of the present invention.

[0058] The heat treatment in step (ii) can be carried out in an inert atmosphere such as nitrogen, an oxygen-containing active atmosphere such as air, or under reduced pressure. It is preferable to carry out the heat treatment in an atmosphere of a gas having a dew point of −40° C. or lower.

[0059] Step (iii) is a step of coating (plating) the liquid crystal polyester multifilament with a metal. Various methods, such as wet and dry methods, can be used for metal coating. Dry metal coating methods include extrusion, sputtering, vapor deposition, and conventional methods. A wet metal coating step can also be carried out by a conventional method, such as a method of attaching a plating catalyst to the surface of the liquid crystal polyester monofilament and then performing electroless plating, or a method of performing electroless plating followed by electrolytic plating.

[0060] The catalyst to be attached may be a metal that has catalytic activity in the electroless plating solution. The metal can be appropriately selected depending on the type of electroless plating solution, and examples include copper, silver, gold, iron, zinc, lead, palladium, nickel, chromium, and tin. These metals can be used alone or in combination of two or more. Examples of methods for applying the catalyst include immersing the liquid crystal polyester multifilament in a catalyst solution containing these metals as metal ions. When copper or nickel is used as the plating metal, a catalyst solution containing palladium ions, preferably a catalyst solution containing tin ions and palladium ions, is preferred.

[0061] The temperature for immersion in the catalyst solution can be appropriately selected depending on the catalyst solution, for example, 20 to 100°C, preferably 25 to 70°C, and the time for immersion in the catalyst solution is, for example, 1 minute to 1 hour, preferably 2 minutes to 30 minutes. After immersion in the catalyst solution, the liquid crystal polyester multifilament to which the catalyst has been attached may be immersed in an accelerator (activation treatment solution) made of an acid to activate the catalyst. The activation treatment can promote the deposition of metal by electroless plating. A conditioner solution or a pre-dip solution may be used to enhance the adhesion between the fiber and the metal.

[0062] Commercially available catalyst solutions can be used, including, for example, the "Surucup" series manufactured by Uemura Kogyo Co., Ltd. [e.g., "Surucup AT-105" (colloidal tin-palladium catalyst) manufactured by Uemura Kogyo Co., Ltd.] and "OPC-80 Catalyst" (colloidal tin-palladium catalyst) manufactured by Okuno Pure Chemical Industries, Ltd.

[0063] As the method for electroless plating, a conventional method can be used, for example, a method of immersing a liquid crystal polyester multifilament to which a catalyst has been attached in an electroless plating solution, etc. Examples of metals to be electrolessly plated include the metals described in the section <Metals>.

[0064] The electroless plating solution may contain, for example, a metal salt as the main component and other additives (for example, a reducing agent, a complexing agent, a leveler, etc.) The temperature of the electroless plating solution can be appropriately selected depending on the type of electroless plating solution and is, for example, 20 to 130°C, preferably 30 to 100°C, and the electroless plating treatment time is, for example, 10 minutes to 20 hours, preferably 15 minutes to 10 hours.

[0065] Commercially available electroless plating solutions can be used, including, for example, electroless copper plating solutions "ATS-ADDCOPPER IW-A," "ATS-ADDCOPPER IW-M," and "ATS-ADDCOPPER IW-C" manufactured by Okuno Pure Chemical Industries, Ltd., electroless gold plating solution "Selfgold OTK-IT," electroless silver plating solution "Dyne Silver EL-3S," and electroless nickel-phosphorus plating solution "Top Nicoron BL80" manufactured by Uemura Kogyo Co., Ltd., and electroless nickel plating solutions "Nimden KTB-3-M" and "Nimden KTB-3-A" manufactured by Uemura Kogyo Co., Ltd. Note that electroless plating can also be followed by, for example, electroplating.

[0066] The uses of the metal-coated polyester multifilament of the present invention are not particularly limited, and it can be widely used in fields where conductive fibers are used, such as smart textiles and electromagnetic wave shielding. In particular, the metal-coated polyester multifilament of the present invention is useful as a smart textile material, for example, an electrode or wiring for a smart textile, because it can achieve both wearability and flex fatigue resistance. [Example]

[0067] The present invention will be described in more detail below with reference to examples, but these examples are not intended to limit the scope of the present invention. Measurement and evaluation methods are shown below.

[0068] <Tensile strength> Under the following conditions, the tensile strength (cN / dtex) of the metal-coated liquid crystal polyester multifilaments obtained in the examples and comparative examples was measured. At this time, since the strength of the plated fiber is mainly determined by the strength of the polyarylate fiber before plating, the tensile strength was calculated based on the original fiber fineness. (Conditions) · Test apparatus: Autograph AGS-100B (manufactured by Shimadzu Corporation) · Test conditions: JIS L1013 · Thread length: 200 mm · Initial load: 0.09 cN / dtex · Tensile speed: 100 mm / min

[0069] <Measurement of Resistance Value and Flexural Fatigue Test> Using a resistance value measuring machine (manufactured by Texio Technology Corporation), the initial resistance value (Ω / 10 cm) of the metal-coated liquid crystal polyester multifilaments obtained in the examples and comparative examples was measured. Then, using a flexural fatigue testing machine (manufactured by Yuasa), the metal-coated liquid crystal polyester multifilament was flexed under the conditions of a flexural angle of 120°, a flexural speed of 60 rpm, a load of 100 g, and a flexural number of 5000 times, and the resistance value was measured again. The specific resistance value was calculated using the following formula, and the flexural fatigue property was evaluated. Specific resistance value = (Resistance value after flexural fatigue test) / (Initial resistance value before flexural fatigue test) For Examples 6 and 7, measurements were also carried out under the condition of a flexural number of 100,000 times.

[0070] <Cross-sectional Observation by X-ray CT> [Calculation of Adhesion Rate] By X-ray CT, 10 cross-sectional photos of the metal-coated liquid crystal polyester multifilaments obtained in the examples and comparative examples were taken at intervals of 50 μm. According to the following judgment criteria, in the 10 cross-sectional photos, the number of adhered fibers and the total number of fibers in the entire cross-sectional photo were counted. Then, the ratio (adhesion rate) of the number of adhered fibers to the total number of fibers was obtained using the following formula.

[0071] Adhesion rate (%) = (Number of adhered fibers) / (Total number of fibers) × 100

[0072] The determination of whether the fibers were stuck or not and the number of stuck fibers were made according to the criteria described in paragraphs

[0036] to

[0042] .

[0073] [Calculating stalemate distance] In the cross-sectional photographs of the metal-coated liquid crystal polyester multifilaments obtained in the Examples and Comparative Examples taken above, the two arbitrarily selected points on the metal surface covering the agglutinated fibers that were the furthest apart were selected, and the distance between the two points was measured. This distance was divided by the diameter of the metal-coated liquid crystal polyester monofilament to determine the distance (agglutination distance) between the two arbitrarily selected points on the metal surface covering the agglutinated fibers relative to the diameter of the metal-coated liquid crystal polyester monofilament.

[0074] <Thread hardness> The yarn hardness of the metal-coated liquid crystalline polyester multifilaments obtained in the examples and comparative examples was measured by the loop method. Specifically, a metal-coated liquid crystalline polyester monofilament was removed from the metal-coated liquid crystalline polyester multifilament, and a loop with a diameter of approximately 30 mm was made as shown in Figure 10, and the longitudinal length a (mm) and lateral length b (mm) were measured. Then, a 1 g weight was hooked to the bottom of the loop, and the longitudinal length a' (mm) and lateral length b' (mm) were measured. Finally, the sum of the longitudinal length displacement and the lateral length displacement was calculated using the following formula, and this was defined as the yarn hardness (or yarn displacement). Yarn hardness (mm) = (a'-a) + (b-b') When using this method, even if the adhesion rate is the same, the smaller the fineness, the greater the thread hardness (thread displacement), and the thinner the thickness of the plating metal, the greater the thread hardness (thread displacement), so a simple comparison is not possible. Therefore, to make corrections, we calculated the thread hardness (corrected value) (m dtex μm) by multiplying the fineness and plating thickness. Yarn hardness (corrected value) (m·dtex·μm) = Yarn hardness (m) × fineness (dtex) × plating thickness (μm) The higher the yarn hardness, the softer the fiber and the greater its flexibility (or softness), which indicates that when used as a smart textile material, the clothing will have excellent wearability.

[0075] <Thickness> The thickness of the metal coating on the metal-coated liquid crystal polyester multifilaments obtained in the examples and comparative examples was measured from the X-ray CT images described above.

[0076] Example 1 (solid-state polymerization) The raw spinning yarn used was a liquid crystal polyester multifilament (product name: Vectran HT, manufactured by Kuraray Co., Ltd.) with a total fineness of 1670 dtex and 300 filaments. The fiber was gradually heated in a nitrogen atmosphere from room temperature to 250°C, and heat-treated for 16 hours to cause solid-state polymerization.

[0077] (Catalyst addition) To wash the surface of the solid-phase polymerized multifilament, 5 ml of Thru-Cup MTE-1-A (Uemura Kogyo Co., Ltd.) was added to 95 ml of ion-exchanged water, and the multifilament cut to 1 m was added and stirred at 50°C for 5 minutes. Next, to assist catalyst adsorption onto the fiber surface, 27 g of Thru-Cup PED-104 (Uemura Kogyo Co., Ltd.) was added to 95 ml of ion-exchanged water, and the washed multifilament was added and stirred at 30°C for 2 minutes. Next, to adsorb the catalyst, 27 g of Thru-Cup PED-104 (Uemura Kogyo Co., Ltd.) and 3 ml of Thru-Cup AT-105 (Uemura Kogyo Co., Ltd.) were added, and the mixture was diluted with ion-exchanged water to 100 ml, after which the adsorption-assisted multifilament was added and washed at 30°C for 8 minutes. Finally, to activate the catalyst, 10 ml of Thrucup AL-106 (manufactured by Uemura Kogyo Co., Ltd.) was added to 90 ml of ion-exchanged water, and the catalyst-adsorbed multifilament was added and stirred for 3 minutes at 25° C. This yielded a liquid crystalline polyester multifilament having the catalyst attached to its surface.

[0078] (Electroless Cu plating) 30 ml of ATS-ADDCOPPER IW-A (Okuno Pure Chemical Industries, Ltd.), 48 ml of ATS-ADDCOPPER IW-M (Okuno Pure Chemical Industries, Ltd.), 6 ml of ATS-ADDCOPPER IW-C, and 516 ml of ion-exchanged water were added, and the catalyst-treated multifilament was added. The mixture was then stirred in a water bath at 42°C for 30 minutes. This resulted in a metal-coated liquid crystalline polyester multifilament comprising a metal-coated liquid crystalline polyester monofilament in which copper was coated on the surface of the liquid crystalline polyester monofilament. FIG. 8 shows an X-ray CT cross-sectional photograph of the resulting metal-coated liquid crystalline polyester multifilament.

[0079] <Example 2> A metal-coated liquid crystal polyester multifilament coated with copper was obtained in the same manner as in Example 1, except that the heat treatment was carried out under conditions of gradually increasing the temperature within a range of room temperature to 270°C.

[0080] Example 3 A metal-coated liquid crystal polyester multifilament coated with copper was obtained in the same manner as in Example 1, except that the heat treatment was carried out under conditions of gradually increasing the temperature within the range of room temperature to 290°C.

[0081] Example 4 A metal-coated liquid crystal polyester multifilament coated with copper was obtained in the same manner as in Example 1, except that a liquid crystal polyester multifilament having a total fineness of 440 dtex and 80 filaments (a spinning raw yarn manufactured by Kuraray Co., Ltd., trade name: Vectran HT) was used as the spinning raw yarn, and the heat treatment conditions were such that the temperature was gradually increased within the range of room temperature to 275°C.

[0082] <Example 5> A metal-coated liquid crystal polyester multifilament coated with copper was obtained in the same manner as in Example 4, except that the heat treatment was carried out under conditions of gradually increasing the temperature within the range of room temperature to 290°C.

[0083] Example 6 Except for changing the plating solution to a nickel plating solution, a metal-coated liquid crystalline polyester multifilament coated with nickel was obtained in the same manner as in Example 3. Also, Fig. 5 shows an X-ray CT cross-sectional photograph of the obtained metal-coated liquid crystalline polyester multifilament.

[0084] (Electroless Ni plating) 90 ml of Nimden KTB-3-M (manufactured by Uemura Kogyo Co., Ltd.), 33 ml of Nimden KTB-3-A (manufactured by Uemura Kogyo Co., Ltd.) and 480 ml of ion-exchanged water were added, and the catalyzed liquid crystal polyester multifilament was added, followed by stirring in a hot water bath at 85°C for 25 minutes.

[0085] Example 7 A metal-coated liquid crystal polyester multifilament coated with nickel was obtained in the same manner as in Example 6, except that a liquid crystal polyester multifilament having a total fineness of 1670 dtex and 50 filaments (a spinning raw yarn manufactured by Kuraray Co., Ltd., trade name: Vectran HT) was used as the spinning raw yarn.

[0086] Example 8 A metal-coated liquid crystal polyester multifilament coated with copper was obtained in the same manner as in Example 1, except that a liquid crystal polyester multifilament having a total fineness of 1580 dtex and 200 filaments (a spinning raw yarn manufactured by Kuraray Co., Ltd., trade name: Vectran UM) was used as the spinning raw yarn.

[0087] Example 9 A metal-coated liquid crystal polyester multifilament coated with copper was obtained in the same manner as in Example 1, except that a liquid crystal polyester multifilament having a total fineness of 560 dtex and 20 filaments (a spinning raw yarn manufactured by Kuraray Co., Ltd., trade name: Vectran HT) was used as the spinning raw yarn.

[0088] <Comparative Example 1> A metal-coated liquid crystal polyester multifilament coated with copper was obtained in the same manner as in Example 1, except that the heat treatment conditions for the raw spun yarn were gradually increased in the range of room temperature to 300°C.

[0089] <Comparative Example 2> A metal-coated liquid crystal polyester multifilament coated with copper was obtained in the same manner as in Example 1, except that the heat treatment conditions for the raw spun yarn were gradually increased in the range of room temperature to 310°C.

[0090] <Comparative Example 3> A metal-coated liquid crystalline polyester multifilament coated with copper was obtained in the same manner as in Example 4, except that the heat treatment conditions for the raw spun yarn were gradually increased in the range of room temperature to 310° C. In addition, Fig. 9 shows an X-ray CT cross-sectional photograph of the obtained metal-coated liquid crystalline polyester multifilament.

[0091] Examples 1 to 9 (Examples 2 to 6 are reference examples) The metal-coated liquid crystalline polyester multifilaments obtained in Comparative Examples 1 to 3 were measured for the conglutination rate, conglutination distance, tensile strength, yarn hardness (yarn displacement), yarn hardness (corrected value), initial resistance, and specific resistance according to the above-mentioned measurement methods, and the results are shown in Table 5. Table 5 also shows the total fineness, number of filaments (number of monofilaments), heat treatment temperature, fineness of the liquid crystalline polyester monofilament (single fiber), plating metal, and plating metal thickness of each metal-coated liquid crystalline polyester multifilament.

[0092] [Table 5]

[0093] As shown in Table 5, the metal-coated liquid crystalline polyester multifilaments of Comparative Examples 2 and 3 have low yarn hardness and low fiber flexibility. Furthermore, the metal-coated liquid crystalline polyester multifilament of Comparative Example 1 has a high specific resistance and low flexural fatigue resistance. Therefore, it was found that the metal-coated liquid crystalline polyester multifilaments obtained in Comparative Examples 1 to 3 are not suitable for use as smart textile materials. In contrast, the metal-coated liquid crystalline polyester multifilaments of Examples 1 to 9 have higher yarn hardness and better fiber flexibility than those of Comparative Examples 2 and 3, and also have lower specific resistance and better resistance to bending fatigue than those of Comparative Example 1. Therefore, it was found that the metal-coated liquid crystalline polyester multifilament of the present invention has excellent wearability and resistance to bending fatigue when used as a smart textile material. Furthermore, when Examples 6 and 7 are compared, the resistivity value after 100,000 flexes is significantly better in Example 7, which has a larger single fiber fineness (thick fiber), and it has also been found that higher flex resistance can be achieved by using thicker polyarylate fibers.

Claims

1. A metal-coated liquid crystal polyester multifilament comprising 2 to 500 metal-coated liquid crystal polyester monofilaments each having a surface coated with a metal having a thickness of 0.1 to 20 μm, the liquid crystal polyester monofilaments having a fineness of 5.0 dtex or more, and in a cross-sectional photograph measured by X-ray CT, the proportion of the number of aggregated fibers to which the metal-coated liquid crystal polyester monofilaments are aggregated is 15% or less relative to the total number of fibers.

2. 2. The metal-coated liquid crystal polyester multifilament according to claim 1, wherein in a cross-sectional photograph measured by X-ray CT, the distance between any two points on the metal surface coating the adhesive fiber is 11 times or less the diameter of the metal-coated liquid crystal polyester monofilament.

3. The metal-coated liquid crystal polyester multifilament according to claim 1 or 2, wherein the tensile strength is 16 cN / dtex or more.

4. The metal-coated liquid crystal polyester multifilament according to any one of claims 1 to 3, wherein the metal comprises at least one selected from the group consisting of copper, silver, gold, iron, zinc, lead, palladium, nickel, chromium, tin, titanium, aluminum, indium, and vanadium.

5. The metal-coated liquid crystal polyester multifilament according to any one of claims 1 to 4, wherein the liquid crystal polyester monofilament has a fineness of 11 dtex or more.

6. The metal-coated liquid-crystalline polyester multifilament according to any one of claims 1 to 5, wherein the specific resistance, which is the ratio of the resistance after a flexural fatigue test to the resistance before the flexural fatigue test, is 25 or less, and the flexural fatigue test is a test in which the metal-coated liquid-crystalline polyester multifilament is bent using a flexural fatigue tester under conditions of a bending angle of 120°, a bending speed of 60 rpm, a load of 100 g, and a number of flexes of 5,000.

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