Polyamide core-sheath composite fiber and fabric

Abstract

Provided is a polyamide core-sheath composite fiber comprising a sheath polymer formed from polyamide and a core polymer formed from polyether ester amide copolymer, wherein the core-sheath composite fiber has a strength of 3.6 cN / dtex or greater, a cross-sectional uniformity ratio d / R of the core-sheath component in the entire yarn of 0.072 or less, and an electrical specific resistance of 107 to 1010 Ω･cm.　The provided polyamide core-sheath composite fiber has a humidity-absorbing property and an antistatic property, and while retaining strength, suppresses generation of fluff and has excellent high-order passability .

Description

[Technical Field]

[0001] The present invention relates to a polyamide sheath-core composite fiber and a fabric, and more particularly to a polyamide sheath-core composite fiber and a fabric that are excellent in moisture absorption and antistatic properties. [Background technology]

[0002] Synthetic fibers made from thermoplastic resins such as polyamide and polyester are widely used in clothing and industrial applications due to their excellent strength, chemical resistance, heat resistance, etc. Polyamide fibers in particular are excellent in properties such as unique softness, high tensile strength, colorability when dyed, and high heat resistance, and are widely used in general clothing applications such as innerwear, outerwear, and sportswear.

[0003] In recent years, with the spread of outdoor sports, demand for sports and casual clothing applications has been increasing year by year. In particular, fabrics used in down jackets and windbreakers require thin, lightweight, soft, and low breathability, and polyamide fibers are becoming increasingly finer and thinner in single yarn size. Polyamide fibers have a tendency to easily become electrostatically charged, and are prone to static electricity in the low temperature and low humidity winter environment. As fabrics become thinner, static electricity is more likely to be generated, and there is a demand for polyamide fibers with excellent antistatic properties.

[0004] Many methods have been proposed for polyamide fibers with excellent antistatic properties, such as adding antistatic agents to fibers or fabrics through post-processing, or combining them with antistatic polymers to create composite fibers. Among these, sheath-core composite polyamide fibers, which use a moisture-absorbing component in the core, have excellent antistatic properties and eliminate the drawbacks of polyamide fibers, which have significant electrical resistance and are easily charged with static electricity. Demand is particularly high for applications such as outerwear worn in the low temperatures and humidity of winter, and research and proposals are underway.

[0005] For example, Patent Document 1 describes a core-sheath conjugate fiber having a polyamide resin sheath and a polyetheresteramide copolymer core, the fiber having a single filament fineness of 3.5 dtex. Patent Document 2 describes a conjugate fiber having a polyamide resin sheath and a polyetheresteramide copolymer core, the core-to-sheath area ratio being 3 / 1 to 1 / 5, and the single filament fineness being 3.25 dtex. Patent Document 3 describes a conjugate fiber having a polyamide core and a polyetheresteramide copolymer core, the core having excellent antistatic properties. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 6-136618 [Patent Document 2] International Publication No. 2014 / 10709 [Patent Document 3] Japanese Patent Application Laid-Open No. 2017-57513 Summary of the Invention [Problem to be solved by the invention]

[0007] However, while the sheath-core composite fibers described in Patent Documents 1 and 2 have excellent moisture absorption and antistatic properties, the raw yarn strength decreases as the fineness and single yarn fineness decrease. Drawing to ensure raw yarn strength leads to frequent occurrence of fuzz in the raw yarn, which not only deteriorates processability in advanced processing steps but also degrades product quality. The sheath-core composite yarn described in Patent Document 3 has excellent antistatic properties, but has a low core ratio of polyetheresteramide copolymer, which ensures moisture absorption. Increasing the core ratio to ensure moisture absorption properties leads to problems, such as a decrease in raw yarn strength and frequent occurrence of fuzz in the raw yarn, which degrades processability in advanced processing steps and product quality, just like Patent Documents 1 and 2.

[0008] As demand for thin, lightweight, soft, and low-breathability woven fabrics increases, fibers and single filaments are becoming finer. Therefore, it is an issue to provide polyamide core-sheath bicomponent fibers that have moisture absorption and antistatic properties, maintain strength, suppress fuzz generation, and have excellent high-order passability. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention has the following configuration. (1) A sheath-core composite multifilament in which the sheath polymer is polyamide and the core polymer is polyether ester amide copolymer, having a strength of 3.6 cN / dtex or more, a cross-sectional uniformity ratio d / R of the core-sheath component in the fiber cross section of 0.072 or less, and an electrical resistivity of 10 7 ~10 10 Polyamide core-sheath composite fiber with a strength of Ω·cm. d: Distance between the center of the inscribed circle of the core component and the center of the inscribed circle of the sheath component R: diameter of the inscribed circle of the sheath component (2) A polyamide sheath-core composite fiber according to (1), having a single fiber fineness of 0.8 to 2.0 dtex and an area ratio of the core in the fiber cross section of 20 to 40%. (3) A fabric having at least a portion thereof the polyamide core-sheath composite fiber according to (1) or (2). [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a polyamide core-sheath composite fiber that has moisture absorption and antistatic properties, suppresses the generation of fluff while maintaining strength, and is excellent in high-order passability. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram showing the cross-sectional shape of a fiber of the present invention. [Figure 2] FIG. 2 is a longitudinal cross-sectional view showing an example of an outlet hole of a composite spinning nozzle used in the present invention. [Figure 3] FIG. 2 is a schematic diagram showing a part of the arrangement of the core component introduction holes and sheath component introduction holes of the lower introduction plate of the composite spinning die used in the present invention. [Figure 4]FIG. 1 is a diagram showing one embodiment of a production apparatus using a direct spinning and drawing method preferably used in the production method of polyamide sheath-core composite fiber of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] The polyamide sheath-core composite fiber of the present invention is a core-sheath composite fiber using a polyamide for the sheath and a polyether ester amide copolymer for the core.

[0013] As shown in FIG. 1, the polyamide core-sheath composite fiber of the present invention has a cross-sectional uniformity ratio (d / R) of 0.072 or less in its cross section. The cross-sectional uniformity ratio here is a value calculated by measuring the distance (d) between the center point of the inscribed circle of the core component (point C) and the center point of the inscribed circle of the sheath component (point S), and the inscribed circle diameter (R) of the sheath component, and is an average value measured for all single yarns. The closer the value is to 0, the more concentric the fiber is, and the larger the value is, the more eccentric the fiber is. By setting the cross-sectional uniformity ratio (d / R) within this range, the generation of fuzz in single yarns is suppressed and the fiber has excellent high-order passability. It is more preferably 0.050 or less. If the cross-sectional uniformity ratio (d / R) exceeds 0.072, the core polyetheresteramide copolymer is eccentric, resulting in uneven sheath thickness in the sheath polyamide. Therefore, when an external force is applied to a thin portion of the sheath, the single yarn is likely to break at that point, causing a large amount of single yarn fluffing, which not only deteriorates the high-order passability but also tends to deteriorate the product quality.

[0014] The polyamide sheath-core composite fiber of the present invention has a strength of 3.6 cN / dtex or more. By setting the strength within this range, yarn breakage during the advanced processing step is reduced and advanced processing ability is improved. In addition, the product durability is excellent. If the strength is less than 3.6 cN / dtex, yarn breakage during the advanced processing step tends to increase and advanced processing ability tends to deteriorate. Furthermore, in clothing applications, mainly outerwear and sportswear, the strength is likely to reach a level that is unsuitable for practical use, and product durability may be poor. A more preferred range is 4.0 cN / dtex or more.

[0015] In the polyamide sheath-core composite fiber of the present invention, the area ratio of the core in the fiber cross section is preferably 20% to 40%. More preferably, it is 20% to 30%, and even more preferably, it is 25% to 30%. Within this range, the sheath can easily absorb a large amount of limited moisture in the air, increasing the rate at which the absorbed moisture is transferred to the core. Furthermore, since the area ratio of the core is small, charged static electricity is quickly transferred through the absorbed core, resulting in excellent moisture absorption and antistatic properties.

[0016] The polyamide sheath-core composite fiber of the present invention has an electrical resistivity of 10 7 ~10 10 Ω·cm. Antistatic properties can be obtained by setting the resistivity in this range. The electrical resistivity of ordinary polyamide fibers is 10 14 The resistance is at the Ω·cm level. Static electricity is affected by the amount of moisture in the air, with static electricity less likely to occur in humid environments and more likely to occur in dry environments. In order to achieve sufficient anti-static properties, a 10 10 A resistivity of Ω·cm or less can provide sufficient antistatic performance. The lower limit of the electrical resistivity that can be achieved by the present invention is 10 7 It is about Ω·cm.

[0017] In the polyamide sheath-core composite fiber of the present invention, ΔMR is preferably 5.0% or more. Setting it in this range ensures moisture absorption. To ensure good comfort when worn, clothing is required to have the function of regulating humidity inside the clothing. ΔMR, which is expressed as the difference in moisture absorption rate between the temperature and humidity inside the clothing, typically 30°C × 90% RH, during light to medium work or light to medium exercise, and the outdoor temperature and humidity, typically 20°C × 65% RH, is used as an index of this humidity regulation. The larger ΔMR, the higher the moisture absorption performance and the better the comfort when worn. A ΔMR of 5.0% or more can suppress stuffiness and stickiness when worn, making it possible to provide clothing with excellent comfort. The upper limit of ΔMR is approximately 17.0%.

[0018] The polyamide sheath-core composite fiber of the present invention can have any total fineness suitable for clothing, preferably 8 to 155 dtex. The single yarn fineness can also be set to any desired value depending on product requirements, but is preferably 0.8 to 2.0 dtex, since the demand for thin, lightweight, soft, and low breathability fabrics has led to a trend toward finer fibers and finer single yarns.

[0019] The polyamide sheath-core composite fiber of the present invention preferably has an elongation of 40% or more, more preferably 42 to 65%. By setting the elongation within this range, yarn breakage during advanced processing steps is reduced and advanced processing ability is improved.

[0020] The polyamide sheath-core composite fiber of the present invention uses a polyamide for the sheath and a polyether ester amide copolymer for the core.

[0021] The polyetheresteramide copolymer used in the core of the present invention is a block copolymer having an ether bond, an ester bond, and an amide bond in the same molecular chain. More specifically, it is a block copolymer obtained by polycondensation reaction of one or more polyamide components (A) selected from lactams, aminocarboxylic acids, and salts of diamines and dicarboxylic acids, and a polyetherester component (B) consisting of a dicarboxylic acid and a poly(alkylene oxide) glycol.

[0022] Examples of the polyamide component (A) include lactams such as ε-caprolactam, dodecanolactam, and undecanolactam; ω-aminocarboxylic acids such as aminocaproic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid; and nylon salts of diamine-dicarboxylic acids, which are precursors of nylon 66, nylon 610, nylon 612, etc., with ε-caprolactam being the preferred polyamide-forming component.

[0023] The polyether ester component (B) comprises a dicarboxylic acid having 4 to 20 carbon atoms and a poly(alkylene oxide) glycol. Examples of dicarboxylic acids having 4 to 20 carbon atoms include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, and dodecadicarboxylic acid; aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid; and alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid. These dicarboxylic acids may be used alone or in combination. Preferred dicarboxylic acids are adipic acid, sebacic acid, dodecadicarboxylic acid, terephthalic acid, and isophthalic acid. Examples of poly(alkylene oxide) glycols include polyethylene glycol, poly(1,2- and 1,3-propylene oxide) glycol, poly(tetramethylene oxide) glycol, and poly(hexamethylene oxide) glycol. Polyethylene glycol, which has excellent moisture absorption properties, is particularly preferred.

[0024] The number-average molecular weight of the poly(alkylene oxide) glycol is preferably 300 to 5,000, more preferably 500 to 4,000. A molecular weight of 300 or more is preferred because it is less likely to scatter outside the system during the polycondensation reaction, resulting in fibers with stable moisture absorption and antistatic properties. Also, a molecular weight of 5,000 or less is preferred because the poly(alkylene oxide) glycol is uniformly dispersed in the polymer, resulting in good moisture absorption and antistatic properties.

[0025] The molar ratio of the polyetherester component (B) in the entire polyetheresteramide copolymer is preferably 20 to 80%. A molar ratio of 20% or more is preferred because good moisture absorption and antistatic properties are obtained. A molar ratio of 80% or less is preferred because good color fastness and washing durability of moisture absorption and antistatic properties are obtained.

[0026] The molar ratio of polyamide to poly(alkylene oxide) glycol is preferably 20% / 80% to 80% / 20%. A poly(alkylene oxide) glycol content of 20% or more is preferred because it provides good moisture absorption and antistatic properties. Furthermore, a poly(alkylene oxide) glycol content of 80% or less is preferred because it provides good color fastness and washing durability of moisture absorption and antistatic properties.

[0027] As such polyether ester amide copolymers, "MH1657" and "MV1074" manufactured by Arkema are commercially available.

[0028] The polyetheresteramide copolymer chips used in the core of the present invention preferably have an orthochlorophenol relative viscosity of 1.2 or more and 2.0 or less. When the orthochlorophenol relative viscosity is 1.2 or more, an optimal stress is applied to the sheath during spinning, which promotes crystallization of the polyamide in the sheath and results in high strength.

[0029] When poly(alkylene oxide) glycol is heated, radicals are generated within the molecule, which then attack adjacent atoms, causing a chain reaction that generates more radicals, and the heat of the reaction can reach temperatures exceeding 200°C.In addition, the smaller the molecular weight of the poly(alkylene oxide) glycol, the easier it is to apply heat to the molecular chain, making it more likely to generate radicals and reaction heat.

[0030] The number-average molecular weight of the poly(alkylene oxide) glycol contained in the polyetheresteramide copolymer used in the present invention is relatively small, at 300 to 5000. Therefore, due to the above-mentioned mechanism, the polyetheresteramide copolymer is prone to thermal degradation, which is very likely to cause hardening and embrittlement of the raw yarn, as well as a decrease in moisture absorption and antistatic properties.

[0031] Therefore, it is preferable to add a hindered phenol-based antioxidant that captures radicals to the polyetheresteramide copolymer core. A half-hindered phenol-based antioxidant is more preferable. The amount of the hindered phenol-based antioxidant added is preferably 1.0% by weight or more and 5.0% by weight or less, based on the weight of the polyetheresteramide copolymer core. More preferably, it is 2.0% by weight or more.

[0032] Examples of doubly hindered phenol-based antioxidants include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (IR1010), tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanuric acid (IR1790), (1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxyphenyl)benzene (AO-330), 1,3,5-tris[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (IR3114), and N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide] (IR1098).

[0033] In the case of both hindered phenol-based antioxidants, thermal degradation of the polyetheresteramide copolymer accelerates due to the heat history during the spinning process (high temperatures applied when the polymer is melted and heat setting after drawing) and the heat history during advanced processing (dyeing and heat setting of the fabric, etc.), significantly reducing the amount of active ingredient in the antioxidant that scavenges remaining radicals in the fabric and clothing. Therefore, to prevent a decrease in the amount of active ingredient in the antioxidant that scavenges remaining radicals in the fabric and clothing, the use of a hindered amine (HALS (hindered amine light stabilizer)) stabilizer in combination with the antioxidant suppresses the thermal degradation of the hindered phenol-based antioxidant, thereby suppressing reaction heat and thermal degradation and preventing hardening, embrittlement, moisture absorption, and deterioration of the raw yarn. Examples of HALS stabilizers include polycondensates of dibutylamine 1,3,5-triazine·N,N-bis(2,2,6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine·N-(2,2,6,6-tetramethyl-4-piperidyl)butylamine (CHIMASSORB2020FDL), 4,7,N,N'-tetrakis[4,6-bis[butyl(1,2,2,6,6-pentamethyl-4-piperidinyl)amine]amine] poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl)((2,2,6,6-tetramethyl-4-piperidyl)imino)hexamethylene((2,2,6,6-tetramethyl-4-piperidyl)imino](CHIMASSORB944).

[0034] Examples of half-hindered phenol-based antioxidants include 2,2′-dimethyl-2,2′-(2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diyl)dipropane-1,1′-diyl bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propanoate] (Sumitomo Chemical Co., Ltd., "Sumilizer" (registered trademark) AG80, ADEKA Corporation, "ADK STAB" (registered trademark) AO-80) and 1,3,5-tris[[4-(1,1-dimethylethyl)-3-hydroxy-2,6-dimethylphenyl]methyl]-1,3,4-triazine-2,4,6(1H,3H,5H)-trione (Solvay Chemical Co., Ltd., Cyanox 1790).

[0035] Compared to doubly hindered phenol-based antioxidants, half-hindered phenol-based antioxidants show very little decrease in the amount of their active ingredients during the heat history during the spinning process and the heat history during advanced processing. Therefore, the use of half-hindered phenol-based antioxidants alone, without the need for a HALS stabilizer as with doubly hindered phenol-based antioxidants, can suppress reaction heat and thermal degradation, as well as hardening and embrittlement of the raw yarn, and deterioration of moisture absorption and antistatic properties. In addition, since the decomposition products of half-hindered phenols are less colored, yellowing can also be suppressed.

[0036] The polyetheresteramide copolymer core may contain other phosphorus-based stabilizers. In addition, various other additives, such as delustering agents, flame retardants, ultraviolet absorbers, infrared absorbers, crystal nucleating agents, fluorescent brighteners, antistatic agents, hygroscopic polymers, and carbon, may be copolymerized or mixed as needed, with the total additive content being 5% by weight or less based on the polyetheresteramide copolymer.

[0037] The ratio of the core is preferably 20% by weight to 40% by weight of the entire composite fiber. It is more preferably 20% by weight to 30% by weight, and even more preferably 25% by weight to 30% by weight. The higher the ratio of the core, the higher the moisture absorption and antistatic properties, but the lower the strength. On the other hand, the lower the ratio of the core, the higher the strength, but the lower the moisture absorption and antistatic properties. By setting the ratio within this range, moisture absorption and antistatic properties are exhibited, and it becomes possible to apply appropriate stretching to the polyamide of the sheath, resulting in high strength.

[0038] Examples of polyamides used for the sheath of the present invention include nylon 6, nylon 66, nylon 46, nylon 9, nylon 610, nylon 11, nylon 12, nylon 612, etc., and copolymer polyamides containing copolymer components such as laurolactam, sebacic acid, terephthalic acid, isophthalic acid, and 5-sodium sulfoisophthalic acid with these polyamides. Among these, nylon 6, nylon 11, nylon 12, nylon 610, and nylon 612 are preferred from the standpoint of spinnability because they have a small difference in melting point with the polyetheresteramide copolymer and can suppress thermal degradation of the polyetheresteramide copolymer during melt spinning. Nylon 6, which has excellent dyeability, is particularly preferred.

[0039] The polyamide sheath may be copolymerized or mixed with various additives, such as delustering agents, flame retardants, antioxidants, ultraviolet absorbers, infrared absorbers, crystal nucleating agents, fluorescent brighteners, antistatic agents, hygroscopic polymers, and carbon, as needed, in a total additive content of 5% by weight or less based on the polyetheresteramide copolymer.

[0040] The polyamide chips used in the sheath of the present invention preferably have a relative viscosity in sulfuric acid of 2.3 to 3.3, which allows the polyamide in the sheath to be appropriately stretched, thereby increasing its strength.

[0041] The melt viscosity of the polyetheresteramide copolymer used in the present invention is 400 to 600 poise, which is lower than the melt viscosity of the polyamide used in the present invention, which is 900 to 1500 poise, and the difference in melt viscosity is also large. Therefore, it is preferable to select a combination of polyetheresteramide copolymer and polyamide having a melt viscosity ratio of 3.0 or less at the spinning temperature. By setting the ratio within this range, the stress applied in the longitudinal direction of the filament during attenuation and drawing after extrusion from the spinneret during spinning is not biased toward the sheath component, and the cross-sectional uniformity ratio (d / R) tends to be small. If the ratio exceeds 3.0, the stress applied in the longitudinal direction of the filament during attenuation and drawing is biased toward the sheath component, resulting in a large cross-sectional uniformity ratio. The melt viscosity referred to here refers to the melt viscosity measured using a capillary rheometer after reducing the moisture content of chip-shaped polymer to 200 ppm or less using a vacuum dryer, and refers to the melt viscosity at the same shear rate at the spinning temperature.

[0042] Furthermore, since the melting point of the polyetheresteramide copolymer is lower than that of the polyamide, it is preferable to select a polyetheresteramide copolymer and a polyamide having a melting point difference of 30°C or less from the viewpoints of suppressing thermal degradation of the polyetheresteramide copolymer during melt spinning and of spinnability.

[0043] In the spinning process, the melting temperature of the core polymer is preferably 235° C. or higher and 260° C. or lower. A melting temperature of the core polymer of 235° C. or higher is preferred because the polyetheresteramide copolymer in the core has a melt viscosity suitable for melt spinning, while a melting temperature of 260° C. or lower is preferred because thermal decomposition of the polyetheresteramide copolymer in the core due to a rise in temperature can be suppressed.

[0044] The melting temperature of the sheath polymer is preferably 240°C or higher and 285°C or lower. When the melting temperature of the sheath polymer is 240°C or higher, the polyamide of the sheath has a melt viscosity suitable for melt spinning, which is preferable. When the melting temperature is 285°C or lower, thermal decomposition of the polyteresteramide copolymer of the core due to temperature rise is suppressed, which is preferable.

[0045] The melting temperature at the confluence is preferably 235°C or higher and 270°C or lower. A temperature of 235°C or higher is preferred because the polyamide and polyetheresteramide copolymer have a melt viscosity suitable for melt spinning. A temperature of 270°C or lower is preferred because thermal decomposition of the polyetheresteramide copolymer can be suppressed.

[0046] In order to control the cross-sectional uniformity ratio (d / R) of the core-sheath composite fiber of the present invention within the above range, it is necessary to optimize the spinneret design until the core-sheath components join together, depending on the melt viscosities of the core component and sheath component polymers.

[0047] Figure 2 is a longitudinal cross-sectional view showing an example of an outlet hole of a conjugate spinning nozzle used for the sheath-core conjugate fiber of the present invention. In Figure 2, the conjugate spinneret is constructed by stacking members in the following order from top to bottom: upper introduction plate 1, lower introduction plate 2, and spinneret plate 3. Below, the conjugate spinneret shown in Figures 2 and 3 will be described along with the flow of polymers from upstream to downstream in the conjugate spinneret.

[0048] The core component polymer flows into the core component introduction hole 1-1 in the upper introduction plate, is metered by the core component throttle 1-2 drilled at the bottom end, and is then discharged into the core component introduction hole 2-1 in the lower introduction plate. Similarly, the core component polymer flowing into the core component introduction hole 2-1 in the lower introduction plate is metered by the core component throttle 2-2 drilled at the bottom end, and then flows into the merging pool 3-1 in the spinneret plate 3.

[0049] The sheath component polymer flows into the sheath component introduction holes 1-3 of the upper introduction plate and is discharged into the sheath component pool 2-3 of the lower introduction plate. The sheath component pool 2-3 of the lower introduction plate, which collects the polymer flowing in from each sheath component introduction hole of the upper introduction plate, has sheath component introduction holes 2-4 drilled on its lower surface for allowing the polymer to flow downstream. The sheath component polymer flowing into the sheath component pool 2-3 is metered by the sheath component throttle section 2-5 drilled at the lower end, and then flows into the merging pool 3-1 of the spinneret plate 3.

[0050] The core polymer and sheath polymer each flow into the confluence pool 3-1 of the die plate 3, and then flow into the discharge hole 3-3 in a core-sheath composite form. They are then metered by the discharge hole throttle section 3-2 drilled at the bottom end and discharged.

[0051] To maintain the metering ability of the core component polymer, it is necessary to measure it twice in total, once at the upper introduction plate 1 and again at the lower introduction plate 2. Because the core component polymer has a low viscosity, measuring the polymer amount twice allows the polymer flow to be controlled and the core component to be centered exactly. Additionally, by measuring it at the upper introduction plate 1, the pressure of the core component polymer is increased, improving the sealing between the upper introduction plate 1 and the lower introduction plate 2, thereby preventing polymer leakage.

[0052] To maintain the metering performance of the sheath component polymer, the relationship between the hole length (L) and hole diameter (D) of the sheath component constriction section 2-5 of the lower introduction plate 2, L / D, must be 1.0 to 2.5. By setting L / D at 1.0 or more, metering performance is stabilized and the cross-sectional uniformity ratio can be kept within this range. If the hole diameter is large and the hole length is small, metering performance decreases and eccentricity is likely to occur. When L / D is less than 1.0, the cross-sectional uniformity ratio (d / R) may exceed 7.2. If the hole diameter (D) is made too small to improve metering performance, clogging with polymer foreign matter becomes more likely, resulting in cross-sectional defects. Furthermore, if the hole length (L) is made too large, the back pressure of the spinneret increases, causing distortion of the spinneret and making the pump unable to withstand the polymer pressure, which can easily lead to polymer leakage. By setting L / D at 2.5 or less, a uniform cross-section can be obtained, enabling stable spinning. A value of 1.5 to 2.5 is even more preferable.

[0053] As shown in Figure 3, the lower introduction plate 2 must be provided with a core introduction hole 2-1 and three sheath introduction holes 2-4 around it. By providing three holes, the sheath polymer can be uniformly filled into the joining pool 3-1 of the spinneret plate 3, and the cross-sectional uniformity ratio can be set within the range. If the number of holes is two or less, the polymer filling into the joining pool 3-1 is likely to be uneven, and the cross-sectional uniformity ratio (d / R) may exceed 7.2. If the number of holes is four or more, it becomes necessary to design the hole diameter (D) to be small or the hole length (L) to be large in order to maintain metering performance. This increases the risk of clogging and leakage, reducing spinning stability and increasing the risk of cross-sectional defects.

[0054] Furthermore, it is preferable that the three sheath component introduction holes 2-4 have the same discharge amount per hole in order to reduce the cross-sectional uniformity ratio (d / R), and therefore it is preferable that the holes be drilled at point symmetrical points, i.e., on the same orbit.

[0055] FIG. 4 shows one embodiment of a production apparatus using a direct spinning and drawing method that is preferably used in the production method of polyamide sheath-core composite fibers of the present invention.

[0056] The polyamide (sheath) and polyetheresteramide copolymer (core) are melted separately, metered and transported by a gear pump, and extruded from the aforementioned conjugate spinneret 4 to form individual filaments. The individual filaments extruded from the conjugate spinneret 4 are cooled to room temperature and solidified by blowing cooling air onto them using a yarn cooling device 5, such as a chimney. Subsequently, an oil is applied in an oil supplying device 6, and the individual filaments are bundled to form a multifilament. The multifilament is then entangled in a fluid entangling nozzle device 7, passed through a take-up roller 8 and a stretching roller 9, and stretched according to the ratio of the peripheral speeds of the take-up roller 8 and the stretching roller 9. The yarn is then heat-treated by heating using the stretching roller 9 and wound up using a winding device.

[0057] In producing the polyamide sheath-core composite fiber of the present invention, the cooling device 5 can be any of a cooling device that blows rectified cooling air from a certain direction, a circular cooling device that blows rectified cooling air from the outer periphery toward the center, or a circular cooling device that blows rectified cooling air from the center toward the outer periphery. The vertical distance Ls from the bottom surface of the spinneret to the top end of the cooling air blowing section of the cooling device 5 (hereinafter referred to as the cooling start distance) is preferably in the range of 159 to 219 mm in order to suppress yarn sway and fiber unevenness, and more preferably 169 to 189 mm. The cooling air speed blown from the cooling air blowing surface is preferably in the range of 20.0 to 40.0 (m / min) on average in the section from the top end surface to the bottom end surface of the cooling air blowing section in order to prevent fineness unevenness and strength.

[0058] In the production of polyamide sheath-core composite fibers of the present invention, the polymer discharged from the spinneret is solidified by blowing cooling air through a cooling device. The fibers are stretched from the solidification position to the oiling position under spinning tension accompanied by an accompanying flow, and then mechanically stretched between a take-up roller and a stretching roller. The sheath-core composite fibers of the present invention are mechanically stretched to promote the orientation and crystallization of the sheath polymer and increase strength, while reducing the spinning tension is key to suppressing the orientation and crystallization of the core polymer and increasing moisture absorption performance. Therefore, the position of the oil supply device 6, i.e., the vertical distance Lg from the bottom of the spinneret to the oil supply nozzle of the oil supply device 6 in Figure 4 (hereinafter referred to as the oil supply position Lg), is preferably 800 to 1500 mm, more preferably 1000 to 1300 mm, depending on the single fiber fineness and the cooling efficiency of the filaments from the cooling device. If the oil supply position is less than 800 mm, the filament will not be cooled sufficiently and will come into contact with the oil supply guide in an unstable structure, resulting in damage, which will not only reduce the filament's single yarn strength but also increase fuzz. The thinner the sheath thickness, the more susceptible it is to damage, as seen in cases with finer single yarn fineness, higher core ratios, and higher cross-sectional uniformity ratios, and the more pronounced the above phenomenon may be. Furthermore, if the oil supply position is greater than 1500 mm, the spinning tension will increase, which will lead to increased orientation and crystallization of the core polymer, reducing moisture absorption performance, and the mechanical draw ratio will decrease, resulting in reduced strength and the possibility of fuzz.

[0059] In the drawing process of the polyamide sheath-core composite fiber of the present invention, the spinning conditions are preferably set so that the product of the speed of the yarn taken up by the take-up roller (spinning speed) and the draw ratio, which is the ratio of the peripheral speeds of the take-up roller and the draw roller, is 3300 or more and 4500 or less. It is more preferably 4000 or less. This value represents the total draw amount by which the polymer discharged from the spinneret is drawn from the spinneret discharge linear speed to the peripheral speed of the take-up roller, and then from the peripheral speed of the take-up roller to the peripheral speed of the draw roller. Setting the draw ratio within this range enables appropriate drawing of the polyamide in the sheath. A draw ratio of 3300 or more is preferred because it promotes crystallization of the polyamide in the sheath, thereby improving the strength of the raw yarn. A draw ratio of 4500 or less is preferred because it promotes moderate crystallization of the polyamide in the sheath, resulting in less yarn breakage and fluffing during spinning.

[0060] As woven fabrics are required to be thin, lightweight, soft, and have low breathability, the fineness of fibers and single filaments has been reduced, resulting in a decrease in the single filament strength of polyamide sheath-core composite fibers, which are made of a polyamide sheath and a polyether ester amide copolymer core. Furthermore, as the area ratio of the core increases and the single filament fineness decreases, the sheath thickness of the polyamide sheath, which is responsible for the single filament strength, becomes thinner, resulting in a decrease in the single filament strength.

[0061] On the other hand, in polyamide monocomponent fibers, in order to ensure the single yarn strength, it is common to appropriately adjust the draw ratio within a range that maintains the elongation required for high-order processing. However, in the polyamide sheath-core composite fiber of the present invention, as the sheath thickness becomes thinner, increasing the draw ratio makes the sheath more prone to rupture, resulting in frequent occurrence of single yarn fluff, and not only impairing high-order passability but also deteriorating product quality. Therefore, it is necessary for the polyamide sheath-core composite fiber of the present invention to have strength and cross-sectional uniformity ratio within these ranges. To achieve this, it is necessary to set production conditions that ensure the strength of the sheath polyamide while uniformizing the sheath thickness.

[0062] Although it depends on the core-sheath composite ratio, single yarn fineness, and the cooling efficiency of the filaments from the cooling device, by setting the oil supply position to 800 to 1500 mm from the spinneret face and the product of the spinning speed and draw ratio to 3300 or more and 4500 or less, optimal stress is applied to the sheath polyamide during spinning, making it possible to apply appropriate draw, which promotes crystallization of the sheath polyamide, and allows the strength to be controlled within this range.

[0063] By using a composite spinneret that is suitable for the flow balance (melt viscosity ratio) of polyamide with a melt viscosity of 900 to 1500 poise and polyetheresteramide copolymer with a melt viscosity of 400 to 600 poise, discharge stability can be ensured and the cross-sectional uniformity ratio can be controlled within this range.

[0064] By adopting such a conjugate spinneret and spinning conditions, it is possible to obtain a sheath-core conjugate fiber having a strength of 3.6 cN / dtex or more, excellent moisture absorption and antistatic properties, and a cross-sectional uniformity ratio d / R of the core-sheath components of all filaments of 0.072 or less. This effect is particularly pronounced when the sheath thickness is relatively thin, the single filament fineness is 2.0 dtex or less, and the core area ratio is 20% or more.

[0065] The core-sheath composite fiber of the present invention has excellent moisture absorption and antistatic properties and can therefore be preferably used for clothing. The fabric form can be selected depending on the purpose, such as woven fabric or knitted fabric. Furthermore, the clothing can be various clothing products such as innerwear and sportswear. [Example]

[0066] The present invention will be described in more detail below with reference to examples, in which the measurement methods for the properties are as follows.

[0067] (1) Relative viscosity of sulfuric acid 0.25 g of chip sample was dissolved in 100 ml of 98 wt% sulfuric acid to make 1 g, and the flow time (T1) was measured at 25 °C using an Ostwald viscometer. Subsequently, the flow time (T2) of 98 wt% sulfuric acid was measured. The ratio of T1 to T2, i.e., T1 / T2, was defined as the relative viscosity of sulfuric acid.

[0068] (2) Orthochlorophenol relative viscosity (OCP relative viscosity) 0.5 g of the chip sample was dissolved in 100 ml of orthochlorophenol to make 1 g, and the flow time (T1) at 25 °C was measured using an Ostwald viscometer. Subsequently, the flow time (T2) of orthochlorophenol was measured. The ratio of T1 to T2, i.e., T1 / T2, was defined as the relative viscosity of sulfuric acid.

[0069] (3) Melt viscosity The chip samples were dried in a vacuum dryer to a moisture content of 200 ppm or less, and the melt viscosity was measured by changing the strain rate stepwise using a Toyo Seiki Capillograph 1B. The measurement temperature was the spinning temperature, and the measurement was performed in a nitrogen atmosphere with a time lapse of 5 minutes from when the sample was placed in the heating furnace to when the measurement started.

[0070] (4) Fineness, single yarn fineness The fiber sample was set on a measuring scale with a rotation of 1.125 m and rotated 200 times to form a looped hank. After drying in a hot air dryer (105±2°C x 60 minutes), the mass of the hank was weighed on a balance and multiplied by the official moisture regain to calculate the fineness. The official moisture regain for core-sheath composite fibers was set to 4.5%.

[0071] (5) Strength and elongation Fiber samples were measured using a "TENSILON" (registered trademark) UCT-100 manufactured by Orientec Co., Ltd. under the constant-rate elongation conditions specified in JIS L1013 (Testing methods for synthetic fiber filament yarns, 2010). Elongation was determined from the elongation at the point showing the maximum strength in the tensile strength-elongation curve. Strength was determined as the value obtained by dividing the maximum strength by the fineness. Measurements were performed 10 times, and the average values ​​were used to determine strength and elongation.

[0072] (6) Cross-sectional uniformity ratio, cross-sectional uniformity A. Taking cross-sectional photographs An embedding agent consisting of paraffin, stearic acid, and ethyl cellulose was dissolved, the fibers were introduced, and the material was left to solidify at room temperature. The raw yarn in the embedding agent was cut in the cross-sectional direction, and the cross-section of the fiber was photographed using a CCD camera (CS5270) manufactured by Tokyo Electronics Co., Ltd., and printed out at 1500x magnification using a color video processor (SCT-CP710) manufactured by Mitsubishi Electric.

[0073] B. Measurement of cross-sectional uniformity ratio As shown in Figure 1, the distance (d) between the center point of the inscribed circle of the core component (point C) and the center point of the inscribed circle of the sheath component (point S) and the diameter of the inscribed circle of the sheath component (R) were measured and calculated. The cross sections of all filaments in the core-sheath composite yarn were measured, and the average value was used as the cross section uniformity ratio.

[0074] C. Cross-sectional uniformity The cross sections of all filaments of the core-sheath composite yarn were visually observed and evaluated according to the following criteria. A: The sheath and core components have a uniform cross section with no variation in circular shape or size. C: The circular shape and size of the sheath and core components vary, resulting in a poor cross section.

[0075] (7) Number of fluffs The fiber sample was rewound at a speed of 500 m / min, and a laser fluff detector was installed 2 mm away from the yarn during rewinding. The total number of defects detected was converted into the number per 100,000 m and displayed. A number of 2 defects or less per 100,000 m was considered to be acceptable.

[0076] (8) Resistivity The fiber sample is thoroughly scoured in a weak alkaline aqueous solution of 0.2% by weight of an anionic surfactant to remove oil and other impurities, then thoroughly rinsed and dried. The sample is then spun into a fiber bundle with a length (L) of 5 cm and a total fineness (D) of 2200 dtex (2000 denier), and left to stand for two days at a temperature of 20°C and a humidity of 40% RH. After this, the resistance of the sample is measured at an applied voltage of 500 V using a vibrating capacitance type micropotential measuring device, and calculated using the following formula. ρ = (R × 0.9D) / (9 × 10 5 ×L×d×10 4 ) ρ: Volume resistivity (Ω cm), R: Resistance (Ω), D: Fineness (dtex), L: Sample length (cm), d: Sample density (g / m) 2 ).

[0077] (9)ΔMR Approximately 1-2 g of fiber sample (or fabric) is weighed into a weighing bottle, dried at 110°C for 2 hours, and the weight is measured (W0). Next, the target substance is kept at 20°C and 65% relative humidity for 24 hours, and then the weight is measured (W65). This is then kept at 30°C and 90% relative humidity for 24 hours, and then the weight is measured (W90). The calculation is then performed using the following formula. MR65=[(W65-W0) / W0]×100% (1) MR90=[(W90-W0) / W0]×100% (2) ΔMR=MR90-MR65 (3).

[0078] (10) Higher order passability The number of times the loom had to be stopped due to thread breakage when 10 plain weave fabrics (1000 m / weft) were woven on a water jet loom with a loom rotation speed of 750 rpm and a weft length of 1620 mm was evaluated according to the following criteria. S: Less than 2 times, A: 2 to 4 times, B: 4 to 6 times, C: 6 or more times S, A, and B were deemed to be process passable.

[0079] [Example 1] (Production of polyamide core-sheath composite fibers) The core used was a polyetheresteramide copolymer chip (manufactured by Arkema, MH1657, orthochlorophenol relative viscosity: 1.69, melting point 200°C, melt viscosity 450 poise (260°C)) in which the polyamide component was nylon 6, the polyether component was polyethylene glycol with a molecular weight of 1500, and the molar ratio of nylon 6 to polyethylene glycol was 24%:76%. In addition, a master chip containing a high concentration of a half-hindered phenolic antioxidant, 2,2'-dimethyl-2,2'-(2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diyl)dipropane-1,1'-diyl bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propanoate] (ADEKA Corporation, Adeka STAB AO-80), was blended with the polyether ester amide copolymer chips in a twin-screw extruder, and the blending amount was adjusted to 3.0% by weight relative to the weight of the core.

[0080] As the polyamide, a titanium oxide-free nylon 6 chip having a sulfuric acid relative viscosity of 2.73, a melting point of 215°C, and a melt viscosity of 1250 poise was used for the sheath.

[0081] The above polyether ester amide copolymer was used as the core, and nylon 6 was used as the sheath. The core was melted at a core melting temperature of 240°C and a sheath melting temperature of 270°C, and the melted fibers were extruded at a spinning temperature of 265°C from a concentric core-sheath composite die having a three-plate structure as illustrated in Figures 2 and 3, two core measurements, three sheath component introduction holes 2-4, a sheath component narrowing section 2-5 of the lower introduction plate 2 for measuring the sheath component with a hole length (L) of 0.3 mm and a hole diameter (D) of 0.2 mm, and 24 discharge holes in the die plate 3, so that the core / sheath ratio (wt%) was 30 / 70.

[0082] Using the multi-component spinning machine shown in Figure 4, the yarn was cooled to room temperature and solidified by passing it through a yarn cooling device with a cooling start distance (Ls) of 100 mm, an air temperature of 18°C, and an air speed of 30 m / min. Subsequently, a water-free oil was applied at an oiling position (Lg) of 1300 mm from the spinneret face, and the individual filaments were bundled to form a multifilament. After oiling with a water-free oil using an oiling device, the multifilament was entangled using a first fluid entangling nozzle device. The multifilament was stretched at a peripheral speed of 3255 m / min (the first take-up roller) and 4167 m / min (the second stretch roller). The stretch ratio was 1.28x and the stretch roller was heat-set at 150°C. The multifilament was then relaxed to 4.0% and wound up at a take-up speed of 4000 m / min, yielding two 22 dtex, 12 filament, sheath-core composite yarns. The raw yarn properties are shown in Table 1.

[0083] (Fabric manufacturing) The core-sheath composite fibers were used as warp and weft yarns, and the warp density was set to 188 threads / 2.54 cm and the weft density to 155 threads / 2.54 cm, and the fabric was woven in a plain weave.

[0084] The resulting greige fabric was scoured in an open soaper using a solution containing 2 g of caustic soda (NaOH) per liter according to conventional methods, dried in a cylinder dryer at 120°C, and then pre-set at 170°C. It was then dyed in a jet dyeing machine using an acid dye (Nylosan Blue-GFL 167% (Sandos) 1.0% owf) at 98°C for 60 minutes, fixed with 3 g / L of synthetic tannin (Nylonfix 501 (Senka)) at 80°C for 20 minutes, dried at 120°C, and finish-set at 175°C. The fabric was then calendered once on both sides (calendering conditions: cylinder calendering, heating roll surface temperature 180°C, heating roll load 147 kN, cloth running speed 20 m / min) to obtain a fabric with a warp density of 210 threads / 2.54 cm and a weft density of 160 threads / 2.54 cm. The resulting fabric was evaluated and the results are shown in Table 1.

[0085] [Examples 2 and 3, Comparative Examples 1 and 2] Spinning was carried out in the same manner as in Example 1, except that in the sheath component constriction section 2-5 of the lower introduction plate 2 for metering the sheath component, L / D was changed as shown in Table 1, to obtain a core-sheath composite yarn, and a woven fabric was produced. The results are shown in Table 1.

[0086] [Comparative Examples 3 to 4] Spinning was carried out in the same manner as in Example 1, except that the spinneret was changed so that the number of core component introduction holes 2-1 and the surrounding sheath component introduction holes 2-4 in the lower introduction plate 2 was changed as shown in Table 1, to obtain core-sheath composite yarns and produce woven fabrics. The results are shown in Table 1.

[0087] Comparative Example 5 Spinning was carried out in the same manner as in Example 1, except that a two-ply spinneret (not shown) was used, the core was metered once, the number of perforations was three, and the L / D of the sheath component constriction section for metering the sheath component was changed as shown in Table 1, to obtain a core-sheath composite yarn and produce a woven fabric. The results are shown in Table 1.

[0088] [Table 1]

[0089] In Examples 1 to 3 of the present invention, the generation of fluff was suppressed and high-order passability was excellent. Comparative Example 1, which had a small L / D of the sheath component narrowing portion of the lower introduction plate that meters the sheath component, Comparative Example 3, which had a small number of perforations, and Comparative Example 5, which had only one core metering, had low metering ability of the polyetheresteramide copolymer, high and biased cross-sectional uniformity ratios, and poor fuzz and high-order passability. Furthermore, Comparative Example 2, which had a large L / D, and Comparative Example 4, which had a large number of perforations, lacked cross-sectional uniformity and had poor spinning stability.

[0090] [Examples 4 to 5, Comparative Examples 6 to 7] Spinning was carried out in the same manner as in Example 1, except that the oil supply position Lg was changed as shown in Table 2 and the spinning speed and draw ratio were adjusted as shown in Table 2, to obtain core-sheath composite yarns and produce woven fabrics. The results are shown in Table 2.

[0091] [Examples 6 to 8] Spinning was carried out in the same manner as in Example 1, except that the core ratio (wt%) was changed as shown in Table 2 and the spinning speed and draw ratio were adjusted as shown in Table 2, to obtain core-sheath composite yarns and prepare woven fabrics. The results are shown in Table 2.

[0092] [Table 2]

[0093] Examples 4 to 8 of the present invention had moisture absorption and antistatic properties, suppressed the generation of fluff while maintaining strength, and were excellent in high-order passability.

[0094] In Comparative Example 6, where the oil supply position Lg was long from below the spinneret, the sheath polyamide could not be stretched appropriately, resulting in decreased strength and increased fuzz, and poor high-order passability. In Comparative Example 7, where the oil supply position Lg was short from below the spinneret, the filaments were not cooled sufficiently, resulting in an unstable structure and damage caused by contact with the oil supply guide, resulting in a slight decrease in strength and increased fuzz, and poor high-order passability. Example 8, which had a high core ratio, had a thinner sheath than Example 1, slightly decreased strength, and slightly increased fuzz, but still achieved acceptable high-order passability.

[0095] [Examples 9 to 10] Spinning was carried out in the same manner as in Example 1, except that the number of discharge holes was changed, the number of filaments was changed as shown in Table 3, and the spinning speed, draw ratio, and oil supply position were adjusted as shown in Table 3, to obtain core-sheath composite yarns and produce woven fabrics. The results are shown in Table 3.

[0096] [Example 11] A sheath-core composite yarn was obtained and a woven fabric was produced in the same manner as in Example 1, except that a nylon 6 chip containing 1.8% titanium oxide, with a relative viscosity in sulfuric acid of 2.63, a melting point of 215°C, and a melt viscosity of 1000 poise, was used as the polyamide sheath, and the spinning speed and draw ratio were adjusted as shown in Table 3. The results are shown in Table 3.

[0097] [Table 3] [Explanation of symbols]

[0098] 1: Upper guide plate 1-1: Core component introduction hole 1-2: Core component narrowing section 1-3:Sheath component introduction hole 2: Lower guide plate 2-1: Core component introduction hole 2-2: Core component narrowing section 2-3: Pod component pool 2-4:Sheath component introduction hole 2-5: Sheath component drawing part 3: Mouthpiece 3-1: Confluence pool 3-2: Discharge hole throttle section 3-3: Discharge hole 4: Spinneret 5: Cooling device 6: Refueling device 7: Fluid entangling nozzle device 8: Pick-up roller 9: Stretching roller 10: Winding device Lg: Refueling position Ls: Cooling start distance

Claims

1. A sheath-core composite multifilament in which the sheath polymer is polyamide and the core polymer is polyether ester amide copolymer has a strength of 3.6 cN / dtex or more, a cross-sectional uniformity ratio d / R of the core-sheath component in the fiber cross section of 0.072 or less, and an electrical resistivity of 10 ７ ~10 １０ Polyamide core-sheath composite fiber with a strength of Ω·cm. d: Distance between the center of the inscribed circle of the core component and the center of the inscribed circle of the sheath component R: diameter of the inscribed circle of the sheath component

2. 2. The polyamide core-sheath composite fiber according to claim 1, wherein the single fiber fineness is 0.8 to 2.0 dtex, and the area ratio of the core in the fiber cross section is 20 to 40%.

3. A fabric comprising at least a portion of the polyamide sheath-core composite fiber according to claim 1 or 2.

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