Sea-island composite polyester fiber

Abstract

The present invention provides a sea-island composite polyester fiber that has at least two types of island regions having different orientations, and that yields a suede-like material that exhibits an excellent raised nap uniformity and an excellent raised nap thickness. A sea-island composite polyester fiber according to the present invention has a sea-island structure that has an island region and at least two different types of island regions. The outer diameter of the island regions is 1.0-7.0 µm; the ratio, for the island regions, of the orientation parameter for the maximally oriented component to the orientation parameter for the minimally oriented component (maximum orientation parameter / minimum orientation parameter) is 1.03-1.15; and the orientation parameter for the maximally oriented component is 4.0-8.5.

Description

[Technical Field]

[0001] The present invention relates to a sea-island composite fiber with many islands made of three or more component polymers. [Background technology]

[0002] Fibers made from thermoplastic polymers such as polyester and polyamide have excellent mechanical properties and dimensional stability, and are therefore widely used not only in clothing but also in interiors, vehicle interiors, industrial applications, etc. As the uses of fibers become more diverse, the required properties also become more diverse, and technologies have been proposed to impart sensory effects such as texture and bulkiness by changing the cross-sectional morphology of the fiber. Among these, "ultrathinning of fibers" has a significant effect on the properties of the fiber itself and the properties after it is made into fabric, and is a mainstream technology from the perspective of controlling the cross-sectional morphology of fibers.

[0003] When spinning a single polymer, even with highly precise control of spinning conditions, the diameter of the resulting fiber is limited to a few micrometers. Therefore, the "island-in-sea type conjugate spinning method," which produces conjugate fibers using a conjugate spinneret, is commonly used. This conjugate spinning method involves arranging multiple island polymers, consisting of a slightly soluble component, in the fiber cross section on a sea polymer, consisting of a soluble component. After forming a fiber or textile product, the sea polymer is removed to produce ultrafine fibers consisting of the island polymers. This conjugate spinning method is widely used in the production of ultrafine fibers currently being produced industrially because it can form a highly accurate, uniform cross-sectional shape of the yarn in the running direction.

[0004] Fibers with extremely fine fibers can exhibit a soft touch and fineness that cannot be obtained with ordinary fibers, and are therefore widely used in clothing applications such as suede-like fabrics and wiping cloths.

[0005] Widely known methods for easily producing ultrafine fibers include using islands-in-sea composite fibers, which contain sparingly soluble island regions in a sea region made of a readily soluble polymer, and split composite fibers, in which sparingly soluble ultrafine fibers are separated by a readily soluble polymer (see, for example, Patent Documents 1 and 2). With these techniques, after being wound up as a composite fiber, the readily soluble polymer is removed by immersing the composite fiber or a fabric product in a solvent, making it possible to obtain sparingly soluble ultrafine fibers.

[0006] In recent years, islands-in-sea type multicomponent composite fibers have been proposed, in which the island portions are composed of two or more types of polymers with different shrinkage ratios, and which, despite being ultrafine fibers, have excellent fiber properties, good spinnability, and, when made into fabrics, have a fluffy feel, flexibility, and a soft texture (see, for example, Patent Document 3). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2005-163234 [Patent Document 2] Japan Special Publication No. 48-28005 [Patent Document 3] Japanese Patent Application Publication No. 2015-183343 Summary of the Invention [Problem to be solved by the invention]

[0008] However, when the composite fibers described in Patent Documents 1 and 2 are used, although they have the soft touch that only ultrafine fibers can provide, the bulkiness and openability of the yarn are low, and when they are made into a suede-like fabric, there are problems with the uniformity and thickness of the raised pile. Also, the composite fiber described in Patent Document 3 has a small difference in shrinkage between different island component fibers, so the bulkiness and openability are low, and when they are made into a suede-like fabric, satisfactory uniformity and thickness of the raised pile are not obtained.

[0009] The present invention aims to solve the above problems and has an object to provide ultrafine fibers that are excellent in openability and bulkiness. [Means for solving the problem]

[0010] To solve the above problems, the present inventors have conducted extensive research and found that a suede-like material excellent in openability and bulkiness can be provided by using a sea-island composite fiber in which island portions with different orientations exhibit differential shrinkage. <1> A sea-island composite polyester fiber having a sea-island structure with a sea portion and two or more different types of island portions, wherein the island portions have an outer diameter of 1.0 to 7.0 μm, and the ratio of the orientation parameter of the maximum orientation component to the orientation parameter of the minimum orientation component of the island portions (maximum orientation parameter / minimum orientation parameter) is 1.03 to 1.15, and the orientation parameter of the maximum orientation component is 4.0 to 8.5. <2> the sea-island composite polyester fiber is subjected to an alkali treatment and a dry heat treatment under the following conditions, and then the yarn length difference of the island parts, which is represented by the following formula (1), is 15 to 40%: <1> The sea-island composite polyester fiber according to the present invention. Alkali treatment conditions: sodium hydroxide aqueous solution (concentration 1g / L), 92°C, 30 minutes, no load Dry heat treatment conditions: 190°C, 1 minute, no load Thread length difference (%)=(L2-L1) / L1×100 ···(1) (In formula (1), L1 is the length of the shortest island, and L2 is the length of the longest island.) <3> The above-mentioned sea portion is made of a copolymer polyester obtained by copolymerizing isophthalic acid or a derivative thereof having a metal sulfonate group with polyalkylene glycol. <1> or <2> The sea-island composite polyester fiber according to claim 1. [Effects of the Invention]

[0011] The sea-island composite polyester fiber of the present invention is a sea-island composite fiber with many islands having two or more types of island portions with different orientations. The sea-island composite polyester fiber of the present invention becomes an ultrafine fiber with excellent openability and bulkiness because the island portions exhibit differential shrinkage due to the treatment of dissolving and removing the sea portion polymer. Therefore, the sea-island composite polyester fiber of the present invention can provide a suede-like material with excellent raised nap uniformity and raised nap thickness and a pleasant feel. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing the island arrangement in the cross section of a composite fiber according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will now be described in further detail. In this specification, a numerical range expressed by "to" is used to mean that the numerical values ​​before and after the range are included as the lower limit and upper limit.

[0014] The sea-island composite polyester fiber of the present invention is an islands-in-sea type composite fiber having a sea-island structure having sea portions and island portions. The polymers constituting the sea-island composite polyester fiber of the present invention contain at least three components, one of which is an easily soluble polymer constituting the sea portion. The island portion is composed of at least two types of hardly soluble polymers with different orientation parameters, and after sea-removal (removal of the sea portion polymer) by alkali treatment and dry heat treatment, there is a difference in fiber length. This results in ultrafine fibers with excellent openability and bulkiness.

[0015] The islands constituting the sea-island composite polyester fiber are preferably made of a polyester-based polymer, such as a polyester obtained by copolymerizing an acid component and a diol component, or polylactic acid.

[0016] Examples of the acid component include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, and dodecanedioic acid, and aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid. Examples of the diol component include alkylene glycols having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, and tetramethylene glycol.

[0017] Particularly preferred polyesters include polyethylene terephthalate, polytrimethylene terephthalate, and polybutylene terephthalate.

[0018] These polyesters may contain copolymerizable components capable of forming other ester bonds in a proportion of 20 mol % or less, more preferably 10 mol % or less, of the diol component and the acid component. Examples of copolymerizable compounds include dicarboxylic acids such as isophthalic acid, succinic acid, cyclohexanedicarboxylic acid, adipic acid, dimer acid, sebacic acid, and 5-sodium sulfoisophthalic acid, and diols such as ethylene glycol, diethylene glycol, butanediol, neopentyl glycol, cyclohexanedimethanol, polyethylene glycol, and polypropylene glycol.

[0019] The polyester polymer may contain additives such as a delustering agent, a flame retardant, an antistatic agent, and a pigment.

[0020] The island portions of the sea-island composite polyester fiber of the present invention use at least two types of polymers with different orientation parameters. By mixing island portions of a highly oriented (high shrinkage) component and a low oriented (low shrinkage) component in the composite fiber, the island portions are opened by the sea-removal treatment, and a mixed yarn of microfibers with different shrinkage is obtained.

[0021] The orientation parameter in the present invention is an index of the molecular orientation of a polymer, and a larger value indicates a higher molecular orientation. The orientation parameter of the island is determined by the Raman spectrum obtained by laser Raman spectroscopy at 1615 cm -1 The intensity of the Raman band originating from the stretching of the carbon-carbon double bond (C=C) of the polyester polymer observed near the fiber axis in the polarization direction perpendicular to the fiber axis and the band at 1730 cm -1 The band intensity ratio is calculated from the band intensity in the polarization direction perpendicular to the fiber axis of the Raman band originating from the stretching of the carbon-oxygen double bond (C=O) of the polyester polymer observed in the vicinity, and the analysis results of the band intensity ratio in the polarization direction perpendicular to the fiber axis of the C=C stretching and C=O stretching of the uniaxially stretched polyester polymer film are used as calibration data, and the band intensity ratio is converted into the orientation parameter shown in the following formula and output to determine the orientation parameter. Band intensity ratio = I 1615 Vertical / I 1730 vertical Orientation parameter = -4.3143 x band intensity ratio + 12.711 (approximation formula when linear correlation is calculated using the analytical results of a uniaxially stretched polyester polymer film as calibration data) Furthermore, high orientation and low orientation refer to the relative high or low orientation of one of two or more types of island portions compared to the other island portions.

[0022] The polymer used in the low shrinkage section is preferably a homopolyester polymer, while the polymer used in the high shrinkage section is preferably a copolymer polyester such as isophthalic acid.

[0023] In the sea-island composite polyester fiber of the present invention, the outer diameter of the island portions is 1.0 to 7.0 μm. By setting the outer diameter of the island portions to 1.0 μm or more, diffused reflection on the fiber surface can be suppressed, and light dyeing can be suppressed when the fiber is made into a fabric. Furthermore, the bending rigidity is increased, resulting in a fabric with high bulk and excellent resilience. On the other hand, by setting the outer diameter of the island portions to 6.1 μm or less, a delicate touch and soft feel can be obtained. The upper limit of the outer diameter of the island portions is preferably 6.5 μm or less, and is preferably 6.3 μm or less, 6.1 μm or less, 5.0 μm or less, and 4.5 μm or less, in that order. The lower limit is preferably 1.5 μm or more, and more preferably 2.0 μm or more.

[0024] In the sea-island composite polyester fiber of the present invention, the ratio of the orientation parameter of the maximum orientation component to the orientation parameter of the minimum orientation component of the island portions (maximum orientation parameter / minimum orientation parameter, hereinafter also referred to as "orientation parameter ratio") is 1.03 to 1.15, and the orientation parameter of the maximum orientation component is 4.0 to 8.5. As described above, the orientation parameter indicates the orientation of molecular chains in each island portion, and a large difference in orientation between island portions and an advanced orientation of high shrinkage portions increases the difference in shrinkage between different island portions. An increase in the difference in shrinkage between island portions results in the appearance of voids after sea removal, enabling improved openability and bulkiness. To achieve the orientation parameter ratio in this range, it is necessary to spin under specific conditions (such as the intrinsic viscosity ratio of the island portions and the composition of the sea portion polymer) as described below, and to control the orientation between island portions. The orientation parameter ratio is more preferably 1.05 to 1.12. The orientation parameter of the maximum orientation component is preferably 4.0 to 8.0, more preferably 4.5 to 8.0, further preferably 5.0 to 7.5, and particularly preferably 6.0 to 7.0.

[0025] From the viewpoint of uniform spreadability and bulkiness, the island parts of the sea-island composite polyester fiber of the present invention are preferably arranged scattered throughout the sea part as shown in Fig. 1. Fig. 1 shows an example in which there are two types of island parts (first island parts 1 and second island parts 2).

[0026] The sea-island composite polyester fiber of the present invention preferably has a yarn length difference of 15 to 40% between the island parts after sea-removal treatment, which is performed by alkali treatment and dry heat treatment under the following conditions. Alkali treatment conditions: sodium hydroxide aqueous solution (concentration 1g / L), 92°C, 30 minutes, no load Dry heat treatment conditions: 190°C, 1 minute, no load If the yarn length difference in the island portions after the sea-removal treatment is 15% or more, the single yarns are easily pulled out during the fabric raising process, resulting in longer pile, improved bulkiness, and a good raised fabric thickness. If the yarn length difference is 40% or less, deterioration in texture (coarseness) due to shrinkage of the entire fabric is suppressed, resulting in a high-quality fabric. The yarn length difference in the island portions after the sea-removal treatment is more preferably 20 to 35%.

[0027] The difference in the island length is calculated by the following formula (1), where L1 is the length of the shortest island and L2 is the length of the longest island in the fiber after alkali treatment and dry heat treatment. When measuring the length of the yarn, a load of 0.1 g / dtex is applied. Thread length difference (%)=(L2-L1) / L1×100 ···(1)

[0028] The sea portion of the sea-island composite polyester fiber is preferably composed mainly of polyester, since alkaline dissolution using caustic soda as a dissolving agent is widely used industrially. More preferably, a copolymer polyester is used in which isophthalic acid or its derivative having a metal sulfonate group is used in combination with polyalkylene glycol, and a combination of 5-sodium sulfoisophthalic acid and polyethylene glycol is particularly preferred.

[0029] The content of isophthalic acid having a metal sulfonate group is preferably 5.0 to 15.0 mol%. When the content of isophthalic acid is 5.0 mol% or more, the elution of the sea portion during sea-removal treatment is improved, and fusion between single yarns due to uneluted sea component is suppressed. Furthermore, when the content of isophthalic acid is 15 mol% or less, softening of the polymer is suppressed, and processability during weaving and knitting is improved.

[0030] The number-average molecular weight of the polyalkylene glycol is preferably 500 to 2000. A number-average molecular weight of 500 or more improves the elution of the sea part during sea-removal treatment, and suppresses fusion between single yarns due to uneluted sea component. Furthermore, the molecular mobility of the sea part during melt spinning is increased, which facilitates the orientation of the island parts, the orientation parameter of the island parts becomes an appropriate value, and a difference in yarn length is expressed, resulting in excellent openability and bulkiness, which is preferable. A number-average molecular weight of the polyalkylene glycol of 2000 or less improves compatibility with polyester, resulting in excellent spinnability.

[0031] The content of polyalkylene glycol in the polyester polymer is preferably 5.0 to 15.0% by weight. When the content of polyalkylene glycol is 5.0% by weight or more, the elution property of the sea part during sea removal is improved, and fusion between single yarns due to uneluted sea part is suppressed. Furthermore, since the molecular mobility of the sea part during melt spinning is increased, the orientation of the island parts is facilitated, the orientation parameter of the island parts becomes an appropriate value, and a difference in yarn length is expressed, resulting in excellent openability and bulkiness, which is preferable. Even if the content of polyalkylene glycol is greater than 15.0% by weight, the effect of improving the elution property of the sea part reaches a plateau.

[0032] Furthermore, when polyester is used as the sea portion, the intrinsic viscosity (hereinafter referred to as IV) of the sea portion polymer is preferably 0.50 to 0.75. If the IV is 0.50 or more, stress to the sea portion increases during spinning, suppressing stress concentration on the island portions. This allows the orientation parameter of each island portion to be an appropriate value, suppressing increase in yarn shrinkage and resulting in a high-quality fabric. On the other hand, if the IV of the sea portion polymer is 0.75 or less, stress concentration to the sea portion during spinning is suppressed, suppressing stress to the island portions to be an appropriate value, thereby resulting in a yarn with excellent openability and bulkiness. This is preferable because the IV of the sea portion polymer is more preferably 0.55 to 0.70.

[0033] Within the scope of the present invention, copolymerization components other than those mentioned above may be copolymerized in an amount of 10 mol % or less with each of the sea polymer and the island polymer. If necessary, inorganic fine particles such as titanium dioxide as a delustering agent and silica fine particles as a lubricant may be added.

[0034] The cross-sectional shape of the island parts of the sea-island composite polyester fiber of the present invention is not particularly limited, and may be, for example, a round cross section, a flat cross section, a lenticular cross section, or any other known modified cross section.

[0035] The number of islands in the sea-island composite polyester fiber of the present invention is preferably 12 to 432 per single yarn. Having 12 or more islands per single yarn allows the island portions to be arranged in the sea portion without gaps, which is preferable because it improves the dimensional stability of the composite fiber. Furthermore, by setting the number of islands per single yarn to 432 or less, it is possible to avoid fusion defects in the island portions. Furthermore, by reducing the difference in contact time between the island portions in the surface layer and the inner layer of the composite fiber with the dissolving agent when dissolving and removing the sea portion, it is possible to reduce the fiber diameter variation of the fibers obtained from the island portions, making it possible to obtain high-strength microfibers. A more preferred range for the number of islands in the composite fiber is 32 to 192 per single yarn.

[0036] In addition, the weight ratio of the sea part in the sea-island composite polyester fiber of the present invention is preferably 10 to 30%. By containing 10% by weight or more of the sea part, fusion between the island parts can be prevented, the efficiency of the sea-part removal process is excellent, and a high-strength, high-quality fabric can be obtained. Furthermore, if the sea part content is 30% by weight or less, the time required for dissolving and removing the sea part can be shortened and the amount of polymer eluted is reduced, thereby increasing the productivity of microfibers, which is preferable. The weight ratio of the sea part in the sea-island composite polyester fiber is more preferably in the range of 15 to 25%.

[0037] Next, an example of the method for producing the sea-island composite polyester fiber of the present invention will be specifically described. The sea-island composite polyester fiber can be produced by either a two-step method in which the extruded polymer is once wound as an undrawn yarn and then drawn to a predetermined breaking elongation in a conventional drawing machine, or a one-step method in which the extruded polymer is once drawn without being taken up. However, in consideration of the quality stability in the fiber longitudinal direction and production stability, the direct spinning and drawing method is the most suitable.

[0038] The spinneret used to produce the fiber can be an existing conjugate spinning spinneret, but it is preferable to use the composite spinneret described in JP 2011-174215 A, which is composed of three major types of laminated members, namely, a metering plate, a distributor plate, and a discharge plate, because it enables the stable production of sea-island composite fibers.

[0039] In order to control the orientation parameter of the islands within this range, it can be preferably controlled by the intrinsic viscosity ratio of the island polymers and the cooling and solidification conditions in addition to the selection of the sea polymer as described above.

[0040] The intrinsic viscosity ratio of the polyester chips in the island portions is preferably 1.2 to 1.6, calculated by dividing the intrinsic viscosity of the high-viscosity component by the intrinsic viscosity of the low-viscosity component. When the intrinsic viscosity ratio is 1.2 or more, the difference in spinning stress applied to the different island portions results in an appropriate orientation parameter ratio, which produces a difference in yarn length and results in a raw yarn with excellent openability and bulkiness. On the other hand, when the intrinsic viscosity ratio is 1.6 or less, stress concentration on the high-viscosity component during spinning is suppressed, the orientation parameter is appropriate, and increased yarn shrinkage is suppressed, resulting in a high-quality fabric.

[0041] In fiber production, the distance from the spinneret discharge surface to the cooling surface (cooling start distance) is preferably 250 to 450 mm to control the cooling solidification of the discharged polymer and to adjust the orientation parameter ratio of different island portions to an appropriate value. The orientation of the island portions is easily affected by differences in viscosity during melting, and if the cooling start distance is 250 mm or more, sufficient melting time is ensured, making it easier for orientation differences to occur between the different island polymers, so the orientation parameter ratio falls within an appropriate range. The longer the cooling start distance, the larger the orientation parameter ratio, but if the cooling start distance is 450 mm or less, the U% value, which indicates yarn unevenness in the longitudinal direction, will be good.

[0042] By applying the above-mentioned content of polyalkylene glycol in the sea portion polymer, number average molecular weight, intrinsic viscosity of the sea portion polymer, intrinsic viscosity ratio of the island portion polymer, and cooling start distance, the orientation parameter of the island portions can be set to an appropriate value, and a difference in yarn length due to a difference in heat shrinkage rate is manifested, thereby providing a sea-island composite polyester fiber that, when made into a fabric, improves openability and bulkiness and enables to obtain raised uniformity and raised thickness that could never be achieved with conventional yarns.

[0043] The sea-island composite polyester fiber of the present invention obtained as described above is preferably used for fabrics and clothing, and the fabric form can be selected depending on the purpose, such as woven fabric, knitted fabric, nonwoven fabric, etc., and clothing is also included. By subjecting the fabric to a nap-raising process, it becomes a luxurious material like suede, and can be suitably used for shirts, blouses, pants, suits, blouses, shoes, bags, base fabrics, etc., depending on the purpose. [Example]

[0044] The present invention will be described in more detail below with reference to examples.

[0045] A. Intrinsic viscosity (IV) The intrinsic viscosity of the polymer was calculated using the following formula (2). The relative viscosity ηr in equation (2) was determined by dissolving 0.8 g of a sample polymer in 10 mL of o-chlorophenol (OCP) with a purity of 98% or higher and using an Ostwald viscometer at 25°C according to the following equation (3): Intrinsic viscosity (IV)=0.0242ηr+0.2634 (2) ηr=η / η0=(t×d) / (t0×d0) ···(3) [In equation (3), η is the viscosity of the polymer solution, η is the viscosity of the OCP, t is the drop time of the solution (seconds), and d is the density of the solution (g / cm 3 ), t0 is the fall time of the OCP (seconds), and d0 is the density of the OCP (g / cm 3 ).

[0046] B. Island orientation parameters The fiber sample was measured by laser Raman spectroscopy, and the peak at 1615 cm -1 The intensity of the Raman band originating from the stretching of the carbon-carbon double bond (C=C) of polyethylene terephthalate (PET) observed near the fiber axis in the polarization direction perpendicular to the fiber axis, and the -1 The band intensity ratio was calculated from the band intensity in the polarization direction perpendicular to the fiber axis of the Raman band originating from the stretching of the carbon-oxygen double bond (C=O) of PET observed in the vicinity. The analysis results of the band intensity ratio in the polarization direction perpendicular to the fiber axis of the C=C stretching and C=O stretching of the uniaxially stretched PET film were used as calibration data, and the band intensity ratio was converted into an orientation parameter and output. Band intensity ratio = I 1615 Vertical / I 1730 vertical Orientation parameter = -4.3143 x band intensity ratio + 12.711 (approximation formula when linear correlation is calculated using the analysis results of uniaxially stretched PET film as calibration data)

[0047] The samples for orientation measurement were embedded in resin (bisphenol-based epoxy resin, cured for 24 hours) and then sectioned using a microtome. The section thickness was 2.0 μm. The section samples were cut at a slight angle from the fiber axis so that the cut surface was elliptical, and measurements were taken at a location where the thickness of the minor axis of the ellipse was constant. Measurements were performed in microscopy mode, with a laser spot diameter of 1 μm at the sample position. Orientation measurements were performed under polarized conditions. The perpendicular condition was defined as when the polarization direction was perpendicular to the fiber axis, and the band intensity ratio was calculated from the Raman band intensities obtained for each. Measurements were performed four times (n = 4) for each island, and the average value was calculated. Detailed conditions are shown below. (Laser Raman spectroscopy) Apparatus: T-64000 (Joobin Yvon / Horiba Jobin Yvon Co., Ltd.) Conditions; Measurement mode; Micro-Raman Objective lens: ×100 Beam diameter: 1 μm Light source: Ar+ laser / 514.5nm Laser power: 50mW Diffraction grating: Single 1800gr / mm Slit: 100μm Detector: CCD / Jobin Yvon 1024×256

[0048] C. Outer diameter of island The cross section of the fiber sample was embedded in epoxy resin and cut using a Reichert-Nissei Ultracut N (ultramicrotome) equipped with a diamond knife. The cut surface was then photographed using a Keyence VHX-2000 microscope. Five single yarns were randomly selected from the photograph, and the major axis of each of four islands (n = 4) per single yarn was measured. The arithmetic mean of the diameters of 20 islands (n = 20) was used as the average island diameter. When the island had a non-circular cross section, the diameter of the circle tangent to the outwardly convex portion of the fiber cross section was calculated as the island diameter.

[0049] D. Strength and elongation Fiber samples were measured in accordance with JIS L1013-2010 - Tensile strength and elongation, and a tensile strength-elongation curve was plotted. The test conditions were a constant-speed extension type tester, a grip distance of 50 cm, and a pulling speed of 50 cm / min. If the tensile strength at break was less than the maximum strength, the maximum tensile strength and the elongation at that time were measured. The strength was calculated using the following formula: Elongation = Elongation at break (%) Strength = Tensile strength at break (cN) / Fineness (dtex)

[0050] E. Fineness The weight per unit length of the fiber sample was measured in an atmosphere of 25°C and 55%RH humidity, and the weight equivalent to 10,000m was calculated from this value. This measurement was repeated 10 times, and the simple average value was rounded off to the nearest whole number to obtain the fineness.

[0051] F. Thread length difference The difference in yarn length was calculated according to the following steps (a) to (c). (a) A single filament of sea-island composite polyester fiber 15 to 20 cm in length was taken, and two knots were marked at approximately 5 cm intervals. Both ends of the filament were then tied and fixed to an appropriate metal frame approximately 10 cm in length. (b) The metal frame prepared in (a) was immersed in a solution capable of dissolving the sea portion of the easily eluted component, and the sea portion was removed. When the easily eluted component was a copolymer polyester combining isophthalic acid or its derivative having a metal sulfonate group with polyalkylene glycol, a sodium hydroxide aqueous solution (concentration 1 g / L) was used as the alkaline aqueous solution. The alkaline aqueous solution was heated to 92°C, and the immersion time was 30 minutes. After that, the metal frame was removed, and the filament sample was washed with raw water. (c) After heat treatment in a dryer at 190°C for 1 minute and cooling, the filament sample was cut along the two knots and disassembled into single islands using tweezers, and each island was measured. The length of the longest island was designated L2 and the length of the shortest island was designated L1, and the yarn length difference was calculated using the following formula (1). When measuring the yarn length, a load of 0.1 g / dtex was applied. Thread length difference (%)=(L2-L1) / L1×100 ···(1)

[0052] G. Fabric evaluation (suede-like fabric) (a) Thickness of the raised nap The thickness of the raised fabric was measured at five random locations in accordance with JIS L1096-2010, 8.4 Thickness (Method A), and the average value was calculated. A raised thickness of 0.16 mm or more was considered acceptable.

[0053] (b) Uniformity of napping The fiber surface of the suede-like fabric was observed using a Keyence VHX-2000 microscope, and the results of the evaluations by five inspectors were relatively evaluated for nap uniformity. The results were calculated by taking the average of the evaluation scores of each inspector and rounding off the decimal point, with the average being rated as S for 5, A for 4, B for 3, and C for 1 to 2. S and A were considered to be acceptable for nap uniformity. <Evaluation criteria> 5 points: Excellent 4 points: slightly better 3 points: Average 2 points: slightly inferior 1 point: Inferior

[0054] (c) Soft touch The softness of the suede-like fabric was evaluated by five highly experienced texture evaluation experts, who then conducted a relative evaluation. The results were calculated by taking the average of the evaluation scores of each expert and rounding off the decimal point, with an average of 5 being S, 4 being A, 3 being B, and 1-2 being C. S and A were considered to be acceptable for softness. <Evaluation criteria> 5 points: Excellent 4 points: slightly better 3 points: Average 2 points: slightly inferior 1 point: Inferior

[0055] (d) Stainability The dyeability (deep dyeability) of suede-like fabric dyed with disperse dyes was evaluated by five inspectors and the results were evaluated relatively. The results were calculated by taking the average of the inspectors' evaluation scores and rounding off the decimal point, with an average of 5 being S, 4 being A, 3 being B, and 1-2 being C. S and A were considered to be acceptable dyeability. (Dyeing conditions) Dye; DinanixNavy S-2G200% 0.3%owf Dyeing assistant: Tetrosin PEC 5.0% owf SunSalt 1.0% owf Bath ratio; 1:100 Dyeing: After processing at 50°C for 15 minutes, the temperature is increased at a rate of 1.6°C / min and processing is continued at 98°C for 20 minutes. <Evaluation criteria> 5 points: Overall dark dyeing, very good 4 points: slightly better 3 points: Average 2 points: slightly inferior 1 point: Overall light dyeing and poor quality

[0056] Example 1 (Manufacturing of sea-island composite polyester fiber) Copolymerized polyethylene terephthalate (PET1) with an IV of 0.67 was prepared as the island A polymer for forming island A, in which isophthalic acid and bisphenol A ethylene oxide adduct were copolymerized at 7.1 mol% and 4.4 mol% of the total acid components, respectively. Polyethylene terephthalate (PET2) with an IV of 0.51 was prepared as the island B polymer for forming island B, with an intrinsic viscosity ratio of 1.31. Easily elutable sea polymer was prepared, in which 8.0 mol% of 5-sodium sulfoisophthalic acid and 9.0 wt% of polyethylene glycol with a number average molecular weight of 1000 were copolymerized. Easily elutable polyethylene terephthalate (PET1) with an IV of 0.69 was prepared.

[0057] The island A polymer, island B polymer, and sea polymer were all melted in an extruder at 265°C, 280°C, and 280°C, respectively, and then metered with a pump to a spinning temperature of 275°C. The mixture was then fed into a spinneret while maintaining the temperature. The weight ratio of island A, island B, and sea was 40 / 40 / 20, and the mixture was fed into a 24-hole sea-island composite spinneret with 48 islands (24 islands for island A and 24 islands for island B). The polymers merged inside the spinneret, and the island polymers (island A polymer, island B polymer) were encased in the sea polymer. As shown in Figure 1, a composite morphology was formed in which island A (first island denoted by reference numeral 1) and island B (second island denoted by reference numeral 2) were interspersed, and the resulting mixture was extruded from the spinneret. The yarn extruded from the spinneret was cooled and solidified by an air cooler so that the cooling start distance was 330 mm, then an oil solution was applied, the yarn was taken up at a speed of 1200 m / min with rolls heated to 90°C, drawn at a draw ratio of 3.3, heat set with rolls heated to 150°C, and then taken up with a winder at a speed of 3950 m / min to obtain a sea-island composite polyester fiber of 70 dtex-12 filaments. The evaluation results of the obtained sea-island composite polyester fiber are shown in Table 1.

[0058] (Suede-like fabric manufacturing) The sea-island composite polyester fiber was then twisted in the S direction at 800 T / m using a double twister twisting machine, and then steam-twisted at 75°C for 30 minutes before being used for warping fabric. The weft yarn was a 56 dtex-24 filament polytrimethylene terephthalate (PTT) / PET bimetal yarn. These warp and weft yarns were used to weave a five-ply satin weave on an air jet loom at a greige density (warp: 222 threads / inch, weft: 97 threads / inch). The resulting woven fabric was then continuously scoured at 98°C, then subjected to a liquid flow relaxation treatment at 130°C, and intermediate set at 180°C. It was then immersed in an aqueous sodium hydroxide solution (1 g / L) to remove the sea element. The resulting fabric was napped using a card cloth napper, and then finish-set at 160°C to produce a suede-like fabric. The evaluation results for the resulting suede-like fabric are shown in Table 1.

[0059] Example 2 A 70 dtex, 12 filament sea-island composite polyester fiber was obtained in the same manner as in Example 1, except that the spinneret was changed so that the number of islands per single yarn was 108 (island part A = 54 islands, island part B = 54 islands), and a suede-like woven fabric was obtained. The evaluation results are shown in Table 1.

[0060] Example 3 A 70 dtex, 12 filament sea-island composite polyester fiber was obtained in the same manner as in Example 1, except that the spinneret was changed so that the number of islands per single yarn was 22 (island part A = 11 islands, island part B = 11 islands), and a suede-like woven fabric was obtained. The evaluation results are shown in Table 1.

[0061] Example 4 A 70 dtex, 12 filament sea-island composite polyester fiber was obtained in the same manner as in Example 1, except that the spinneret was changed so that the number of islands per single yarn was 432 (island part A = 216 islands, island part B = 216 islands), and a suede-like woven fabric was obtained. The evaluation results are shown in Table 1.

[0062] Example 5 A 70 dtex, 12 filament sea-island composite polyester fiber was obtained in the same manner as in Example 1, except that the spinneret was changed so that the number of islands per single yarn was 12 (island part A = 6 islands, island part B = 6 islands), and a suede-like woven fabric was obtained. The evaluation results are shown in Table 1.

[0063] Example 6 A 70 dtex, 12 filament sea-island composite polyester fiber was obtained in the same manner as in Example 1, and a suede-like woven fabric was obtained, except that polyethylene terephthalate (PET3) with an IV of 0.56 was prepared as the island B polymer for forming the island B, so that the intrinsic viscosity ratio was 1.20. The evaluation results are shown in Table 1.

[0064] Example 7 A 70 dtex, 12 filament sea-island composite polyester fiber and a suede-like woven fabric were obtained in the same manner as in Example 1, except that a copolymerized polyethylene terephthalate (PET4) with an IV of 0.82, in which isophthalic acid and an ethylene oxide adduct of bisphenol A were copolymerized in amounts of 7.1 mol % and 4.4 mol %, respectively, based on the total acid components, was prepared as the island portion A polymer for forming the island portion A, so that the intrinsic viscosity ratio was 1.60. The evaluation results are shown in Table 1.

[0065] Example 8 A 70 dtex, 12 filament sea-island composite polyester fiber and a suede-like woven fabric were obtained in the same manner as in Example 1, except that an alkali-elutable polyethylene terephthalate (easily elutable PET2) with an IV of 0.50 containing a copolymer of 8.0 mol% of 5-sodium sulfoisophthalic acid and 9.0 wt% of polyethylene glycol having a number average molecular weight of 1,000 was used as the easily elutable sea polymer. The evaluation results are shown in Table 2.

[0066] Example 9 A 70 dtex, 12 filament sea-island composite polyester fiber and a suede-like woven fabric were obtained in the same manner as in Example 1, except that an alkali-elutable polyethylene terephthalate (easily elutable PET3) with an IV of 0.75 containing a copolymer of 8.0 mol% of 5-sodium sulfoisophthalic acid and 9.0 wt% of polyethylene glycol having a number average molecular weight of 1,000 was used as the easily elutable sea polymer. The evaluation results are shown in Table 2.

[0067] Example 10 A 70 dtex, 12 filament sea-island composite polyester fiber and a suede-like woven fabric were obtained in the same manner as in Example 1, except that an alkali-elutable polyethylene terephthalate (easily elutable PET4) with an IV of 0.69 containing a copolymerized component of 8.0 mol% of 5-sodium sulfoisophthalic acid and 9.0 wt% of polyethylene glycol having a number average molecular weight of 500 was used as the easily elutable sea polymer. The evaluation results are shown in Table 2.

[0068] Example 11 A 70 dtex, 12 filament sea-island composite polyester fiber and a suede-like woven fabric were obtained in the same manner as in Example 1, except that an alkali-elutable polyethylene terephthalate (easily elutable PET5) with an IV of 0.69 containing a copolymer of 8.0 mol% of 5-sodium sulfoisophthalic acid and 9.0 wt% of polyethylene glycol having a number average molecular weight of 2000 was used as the easily elutable sea polymer. The evaluation results are shown in Table 2.

[0069] Example 12 A 70 dtex, 12 filament sea-island composite polyester fiber and a suede-like woven fabric were obtained in the same manner as in Example 1, except that an alkali-elutable polyethylene terephthalate (easily elutable PET6) with an IV of 0.69 containing a copolymerized component of 8.0 mol% of 5-sodium sulfoisophthalic acid and 5.0 wt% of polyethylene glycol having a number average molecular weight of 1,000 was used as the easily elutable sea polymer. The evaluation results are shown in Table 2.

[0070] Example 13 A 70 dtex, 12 filament sea-island composite polyester fiber and a suede-like woven fabric were obtained in the same manner as in Example 1, except that an alkali-elutable polyethylene terephthalate (easily elutable PET7) with an IV of 0.69 containing a copolymerized component of 8.0 mol% of 5-sodium sulfoisophthalic acid and 15.0 wt% of polyethylene glycol having a number average molecular weight of 1,000 was used as the easily elutable sea polymer. The evaluation results are shown in Table 2.

[0071] [Table 1]

[0072] [Table 2]

[0073] Comparative Example 1 A 70 dtex, 12 filament sea-island composite polyester fiber was obtained in the same manner as in Example 1, except that the spinneret was changed so that the number of islands per single yarn was 720 (island part A = 360 islands, island part B = 360 islands), and a suede-like woven fabric was obtained. The evaluation results are shown in Table 3.

[0074] The sea-island composite polyester fiber of Comparative Example 1 had a small fiber outer diameter of 0.8 μm after sea-removal, so the suede-like fabric was lightly dyed overall and had poor dyeability.

[0075] Comparative Example 2 A 70 dtex, 12 filament sea-island composite polyester fiber was obtained in the same manner as in Example 1, except that the spinneret was changed so that the number of islands per single yarn was 8 (island part A = 4 islands, island part B = 4 islands), and a suede-like woven fabric was obtained. The evaluation results are shown in Table 3.

[0076] The sea-island composite polyester fiber of Comparative Example 2 had a large fiber outer diameter of 7.5 μm after sea-removal, and therefore the suede-like fabric had a hard texture and poor soft touch.

[0077] Comparative Example 3 A 70 dtex, 12 filament sea-island composite polyester fiber was obtained in the same manner as in Example 1, and a suede-like woven fabric was obtained, except that polyethylene terephthalate (PET5) with an IV of 0.60 was prepared as the island B polymer for forming the island B, so that the intrinsic viscosity ratio was 1.12. The evaluation results are shown in Table 3.

[0078] The sea-island composite polyester fiber of Comparative Example 3 had a low orientation parameter of the maximum oriented component and a low ratio of the orientation parameter of the maximum oriented component to the orientation parameter of the minimum oriented component (orientation parameter ratio), and a small yarn length difference, so the suede-like fabric was inferior in raised thickness and raised uniformity.

[0079] Comparative Example 4 A 70 dtex, 12 filament sea-island composite polyester fiber and a suede-like woven fabric were obtained in the same manner as in Example 1, except that a copolymerized polyethylene terephthalate (PET6) having an IV of 0.90, in which isophthalic acid and an ethylene oxide adduct of bisphenol A were copolymerized in amounts of 7.1 mol % and 4.4 mol %, respectively, based on the total acid components, was prepared as the island portion A polymer for forming the island portion A, so that the intrinsic viscosity ratio was 1.76. The evaluation results are shown in Table 3.

[0080] The sea-island composite polyester fiber of Comparative Example 4 had a high orientation parameter and orientation parameter ratio of the maximum orientation component, and the yarn shrinkage was too large, so the texture of the suede-like woven fabric was hard and the soft touch was poor.

[0081] Comparative Example 5 A 70 dtex, 12 filament sea-island composite polyester fiber and a suede-like woven fabric were obtained in the same manner as in Example 1, except that an alkali-elutable polyethylene terephthalate (easily elutable PET8) with an IV of 0.40 containing a copolymer of 8.0 mol% of 5-sodium sulfoisophthalic acid and 9.0 wt% of polyethylene glycol having a number average molecular weight of 1,000 was used as the easily elutable sea polymer. The evaluation results are shown in Table 3.

[0082] The sea-island composite polyester fiber of Comparative Example 5 had a high orientation parameter and orientation parameter ratio of the maximum orientation component, and the yarn shrinkage was too large, so the texture of the suede-like woven fabric was hard and the soft touch was poor.

[0083] Comparative Example 6 A 70 dtex, 12 filament sea-island composite polyester fiber and a suede-like woven fabric were obtained in the same manner as in Example 1, except that an alkali-elutable polyethylene terephthalate (easily elutable PET9) with an IV of 0.80 containing a copolymer of 8.0 mol% of 5-sodium sulfoisophthalic acid and 9.0 wt% of polyethylene glycol having a number average molecular weight of 1,000 was used as the easily elutable sea polymer. The evaluation results are shown in Table 3.

[0084] The sea-island composite polyester fiber of Comparative Example 6 had a low orientation parameter of the maximum orientation component and a small yarn length difference, and therefore the suede-like fabric was inferior in raised thickness and raised uniformity.

[0085] Comparative Example 7 A 70 dtex, 12 filament sea-island composite polyester fiber and a suede-like woven fabric were obtained in the same manner as in Example 1, except that an alkali-elutable polyethylene terephthalate (easily elutable PET10) with an IV of 0.69 containing a copolymer of 8.0 mol% of 5-sodium sulfoisophthalic acid and 9.0 wt% of polyethylene glycol having a number average molecular weight of 4000 was used as the easily elutable sea polymer. The evaluation results are shown in Table 3.

[0086] The sea-island composite polyester fiber of Comparative Example 7 had a low orientation parameter of the most oriented component and a small yarn length difference, so the suede-like fabric was inferior in raised thickness and raised uniformity. In addition, the yarn strength was low, and the suede-like fabric was inferior in durability.

[0087] Comparative Example 8 A 70 dtex, 12 filament sea-island composite polyester fiber and a suede-like woven fabric were obtained in the same manner as in Example 1, except that an alkali-elutable polyethylene terephthalate (easily elutable PET11) with an IV of 0.69 containing a copolymerized component of 8.0 mol% of 5-sodium sulfoisophthalic acid and 3.0 wt% of polyethylene glycol having a number average molecular weight of 1,000 was used as the easily elutable sea polymer. The evaluation results are shown in Table 3.

[0088] The sea-island composite polyester fiber of Comparative Example 8 had a low orientation parameter of the maximum orientation component and a small yarn length difference, and therefore the suede-like fabric was inferior in raised thickness and raised uniformity.

[0089] Comparative Example 9 A 70 dtex, 12 filament sea-island composite polyester fiber was obtained, and a suede-like woven fabric was also obtained in the same manner as in Example 1, except that an alkali-elutable polyethylene terephthalate (easily elutable PET12) with an IV of 0.55 containing a component copolymerized with 5-sodium sulfoisophthalic acid at 5.0 mol% was used as the easily elutable sea polymer. The evaluation results are shown in Table 3.

[0090] The sea-island composite polyester fiber of Comparative Example 9 had a low orientation parameter and orientation parameter ratio of the most oriented component and a small yarn length difference, so the suede-like fabric had poor raised thickness and raised uniformity. In addition, the yarn strength was low, and the suede-like fabric had poor durability.

[0091] Comparative Example 10 A 70 dtex, 12 filament sea-island composite polyester fiber and a suede-like woven fabric were obtained in the same manner as in Example 1, except that the cooling start distance of the yarn extruded from the spinneret was set to 200 mm. The evaluation results are shown in Table 3.

[0092] The sea-island composite polyester fiber of Comparative Example 10 had a low orientation parameter of the maximum orientation component and a small yarn length difference, and therefore the suede-like fabric was inferior in raised thickness and raised uniformity.

[0093] [Table 3]

[0094] Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications and variations are possible without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2020-193153) filed on November 20, 2020, the entire contents of which are incorporated by reference. [Explanation of symbols]

[0095] 1: First island (Island A) 2: Second island (island B)

Claims

1. A sea-island composite polyester fiber having a sea-island structure with a sea portion and two or more types of island portions having different orientations, wherein the island portions have outer diameters of 1.0 to 7.0 μm, and the ratio of the orientation parameter of the maximum oriented component to the orientation parameter of the minimum oriented component of the island portions (maximum orientation parameter / minimum orientation parameter) is 1.05 to 1.15, and the orientation parameter of the maximum oriented component is 5.0 to 8.

5.

2. 2. The sea-island composite polyester fiber according to claim 1, wherein after the sea-island composite polyester fiber is subjected to an alkali treatment and a dry heat treatment under the following conditions, a yarn length difference of the island parts, represented by the following formula (1), is 20 to 40%: Alkali treatment conditions: sodium hydroxide aqueous solution (concentration 1 g / L), 92°C, 30 minutes, no load Dry heat treatment conditions: 190°C, 1 minute, no load Yarn length difference (%) = (L2-L1) / L1 x 100...(1) (In formula (1), L1 is the length of the shortest island portion, and L2 is the length of the longest island portion.)

3. 3. The sea-island composite polyester fiber according to claim 1, wherein the sea portion comprises a copolymer polyester obtained by copolymerizing isophthalic acid or a derivative thereof having a metal sulfonate group with polyalkylene glycol having a number average molecular weight of 500 to 2,000.

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