Sea-island composite polyester fiber

Abstract

The present invention provides a sea-island composite polyester fiber having two or more island portions with different orientations, which can be used as a suede-like conditioning material with excellent nap uniformity and nap thickness. The sea-island composite polyester fiber of the present invention has an island structure comprising a sea portion and two or more different island portions, wherein the outer diameter of the island portions is 1.0 to 7.0 μm, the ratio of the orientation parameter of the maximum oriented component to the orientation parameter of the minimum oriented component (maximum orientation parameter / minimum orientation parameter) of the island portions is 1.03 to 1.15, and the orientation parameter of the maximum oriented component is 4.0 to 8.5.

Description

Technical Field

[0001] The present invention relates to a multi-island sea-in-a-sea composite fiber made of three or more polymer components. Background Art

[0002] Fibers made of thermoplastic polymers such as polyester and polyamide are widely used not only in clothing but also in interiors, vehicle interiors, and industrial applications due to their excellent mechanical properties and dimensional stability. As fiber applications diversify, the required properties are also becoming more diverse, leading to the development of technologies that can enhance sensory effects such as hand and bulkiness through the cross-sectional morphology of fibers. Among these technologies, "fiber micronization" is a mainstream approach, as it significantly impacts the properties of the fiber itself and the properties of fabrics made from it, and allows for the control of fiber cross-sectional morphology.

[0003] When spinning polymers individually, even with highly controlled spinning conditions, the resulting fiber diameter is limited to a few microns. Therefore, the "island-in-the-sea composite spinning method," which produces composite fibers through a composite nozzle, is commonly used. This composite spinning method arranges multiple island polymers, composed of insoluble components, within a sea polymer composed of readily soluble components within the fiber cross-section. After forming the fiber or fiber product, the sea polymers are removed to produce ultrafine fibers composed of the island polymers. This composite spinning method is widely used in the industrial production of ultrafine fibers because it can produce a uniform and highly precise cross-sectional morphology in the direction of fiber travel.

[0004] Fibers with extreme fineness can produce a soft touch and fine texture that cannot be achieved with ordinary fibers. Therefore, they are widely used in clothing applications as suede-like fabrics and wipes.

[0005] As methods for easily producing ultrafine fibers, sea-island composite fibers utilizing a sea portion composed of a readily soluble polymer containing an insoluble island portion, and split-fiber composite fibers in which insoluble ultrafine fibers are separated by readily soluble polymers, are well known (for example, see Patent Documents 1 and 2). In these techniques, after the composite fibers are formed and wound, the composite fibers or fabric product are immersed in a solvent to remove the readily soluble polymer, thereby obtaining insoluble ultrafine fibers.

[0006] In addition, in recent years, sea-island type multi-component composite fibers have been proposed, in which the island portion is composed of two or more polymers with differential shrinkage, and which, although being ultrafine fibers, have excellent fiber properties, good spinning properties, and have a bulky feel, softness, and a soft hand feel when made into fabric (for example, see Patent Document 3).

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 2005-163234

[0010] Patent Document 2: Japanese Patent Publication No. 48-28005

[0011] Patent Document 3: Japanese Patent Application Laid-Open No. 2015-183343 Summary of the Invention

[0012] Problems to be solved by the invention

[0013] However, when using the conjugate fibers described in Patent Documents 1 and 2, while they have a soft touch unique to ultrafine fibers, they have low bulk and fiber-opening properties, resulting in problems with nap uniformity and thickness when used in suede-like fabrics. Furthermore, the conjugate fibers described in Patent Document 3 also have low bulk and fiber-opening properties due to the small difference in shrinkage between the island components. Consequently, satisfactory nap uniformity and thickness cannot be achieved when used in suede-like fabrics.

[0014] The present invention solves the above-mentioned problems and aims to provide ultrafine fibers having high fiber opening properties and excellent bulkiness.

[0015] Methods for solving problems

[0016] To solve the above-mentioned problems, the present inventors conducted intensive research and found that a suede-like conditioning material with excellent fiber opening and bulkiness can be provided by using sea-island composite fibers that exhibit differential shrinkage due to island portions with different orientations. Specifically, the present invention employs the following configuration.

[0017] <1> A sea-island composite polyester fiber having a sea-island structure, wherein the sea-island structure comprises a sea portion and two or more different island portions, wherein the outer diameter of the island portion is 1.0 to 7.0 μm, the ratio of the orientation parameter of the maximum orientation component of the island portion to the orientation parameter of the minimum orientation component (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.

[0018] <2> The sea-island composite polyester fiber according to <1>, wherein the fiber length difference of the island portion represented by the following formula (1) is 15 to 40% after the sea-island composite polyester fiber is subjected to an alkali treatment and a dry heat treatment under the following conditions.

[0019] 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

[0020] Wire length difference (%) = (L2-L1) / L1×100···(1)

[0021] (In formula (1), L1 is the length of the shortest island portion, and L2 is the length of the longest island portion.)

[0022] <3> The sea-island composite polyester fiber according to <1> or <2> above, wherein the sea portion comprises a copolyester obtained by copolymerizing isophthalic acid or a derivative thereof having a metal sulfonate group with polyalkylene glycol.

[0023] Effects of the Invention

[0024] The sea-island composite polyester fiber of the present invention is a multi-island composite fiber having two or more island portions with different orientations. Since the island portions exhibit differential shrinkage due to the dissolution and removal of the sea portion polymer, the sea-island composite polyester fiber of the present invention becomes an ultrafine fiber with excellent fiber opening and bulkiness. Therefore, the sea-island composite polyester fiber of the present invention can provide a suede-like material with excellent tactile quality and raised nap uniformity and thickness. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram showing the arrangement of island portions in a cross section of a composite fiber according to an embodiment of the present invention. DETAILED DESCRIPTION

[0026] Hereinafter, the present invention will be described in further detail.

[0027] In addition, in this specification, the numerical range shown by "to" is used to mean that the numerical values ​​before and after it are included as the lower limit and the upper limit.

[0028] The sea-island composite polyester fiber of the present invention is a sea-island composite fiber having a sea portion and an island portion.

[0029] The polymers that comprise the sea-island composite polyester fiber of the present invention comprise at least three components, one of which is a readily soluble polymer that forms the sea portion. The island portion is composed of at least two poorly soluble polymers with different orientation parameters. After sea removal (removal of the sea portion polymer) through alkali treatment and dry heat treatment, the fibers exhibit a difference in fiber length. This results in ultrafine fibers with excellent openability and bulkiness.

[0030] It is preferred to use a polyester polymer in the island portions constituting the sea-island composite polyester fiber of the present invention. Examples of the polyester polymer include polyesters obtained by copolymerizing an acid component and a diol component, and polylactic acid.

[0031] 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, 1,3-propylene glycol, and 1,4-butanediol.

[0032] Particularly preferred examples of polyester include polyethylene terephthalate, polypropylene terephthalate, and polybutylene terephthalate.

[0033] These polyesters may contain other copolymerizable components capable of forming ester bonds in a proportion of 20 mol% or less, more preferably 10 mol% or less, of each 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 sulfoisophthalate; and glycols such as ethylene glycol, diethylene glycol, butanediol, neopentyl glycol, cyclohexanedimethanol, polyethylene glycol, and polypropylene glycol.

[0034] The polyester polymer may contain additives such as a matting agent, a flame retardant, an antistatic agent, and a pigment.

[0035] The island portions of the sea-island composite polyester fiber of the present invention utilize at least two polymers having different orientation parameters. By mixing island portions containing a highly oriented (high shrinkage) component and a low oriented (low shrinkage) component in the composite fiber, the island portions are opened by sea removal treatment, resulting in a mixed yarn having microfibers with different shrinkage.

[0036] The orientation parameter in the present invention is an index of the molecular orientation of the polymer. A larger value indicates a higher molecular orientation. The orientation parameter of the island portion is obtained as follows: In the Raman spectrum obtained by laser Raman spectroscopy, the orientation parameter at 1615 cm -1 The intensity of the Raman band derived from the stretching of the carbon-carbon double bond (C=C) of the polyester polymer in the polarization direction perpendicular to the fiber axis is observed near 1730 cm -1 The band intensity ratio is calculated from the band intensity of the Raman band of the stretching of the carbon-oxygen double bond (C=O) of the polyester polymer confirmed nearby in the polarization direction perpendicular to the fiber axis. The analysis results of the band intensity ratio of the C=C stretching and C=O stretching of the uniaxially stretched film of the polyester polymer in the polarization direction perpendicular to the fiber axis are used as calibration data, and the band intensity ratio is converted into the orientation parameter shown in the following formula and output.

[0037] Band intensity ratio = I 1615 Vertical / I 1730 vertical

[0038] Orientation parameter = -4.3143 × band intensity ratio + 12.711 (approximate formula obtained by linear correlation using the analysis results of uniaxially stretched polyester polymer films as calibration data)

[0039] Furthermore, the terms "high orientation" and "low orientation" mean that the orientation of one of two or more island portions is relatively higher or lower than that of the other island portions.

[0040] As the polymer used in the low shrinkage portion, a homopolyester polymer is suitable. On the other hand, as the polymer used in the high shrinkage portion, a copolyester such as isophthalic acid is preferred.

[0041] In the sea-island composite polyester fiber of the present invention, the outer diameter of the island portion is 1.0 to 7.0 μm. By setting the outer diameter of the island portion to 1.0 μm or greater, diffuse reflection on the fiber surface can be suppressed, thereby preventing fading of the dye when the fabric is formed. Furthermore, the bending rigidity is increased, resulting in a fabric with a bulky and excellent resilience. On the other hand, by setting the outer diameter of the island portion to 6.1 μm or less, a delicate and soft feel can be achieved. The outer diameter of the island portion preferably has an upper limit of 6.5 μm or less, with the following lower limits being preferably 6.3 μm or less, 6.1 μm or less, 5.0 μm or less, and 4.5 μm or less, respectively. The lower limit is preferably 1.5 μm or greater, and more preferably 2.0 μm or greater.

[0042] The ratio of the orientation parameter of the maximum oriented component in the island portion of the sea-island composite polyester fiber of the present invention to the orientation parameter of the minimum oriented component (maximum orientation parameter / minimum orientation parameter, hereinafter also referred to as the "orientation parameter ratio") is 1.03 to 1.15, and the orientation parameter of the maximum oriented component is 4.0 to 8.5. As described above, the orientation parameter represents the orientation of the molecular chains in each island portion. Large orientation differences between island portions, and large shrinkage differences between island portions with different orientation progressions in high shrinkage portions, increase the shrinkage differences between island portions. By increasing the shrinkage differences between island portions, voids appear after sea removal, which can improve fiber opening and bulkiness. To achieve this range of the orientation parameter ratio, spinning under specific conditions (such as the intrinsic viscosity ratio of the island portions and the composition of the sea portion polymer) is necessary to control the orientation between the island portions. The orientation parameter ratio is more preferably 1.05 to 1.12. Furthermore, the orientation parameter of the maximum oriented component is preferably 4.0 to 8.0, more preferably 4.5 to 8.0, even more preferably 5.0 to 7.5, and particularly preferably 6.0 to 7.0.

[0043] From the viewpoint of uniform fiber opening and bulkiness, the arrangement of the island portions of the sea-island composite polyester fiber of the present invention is as follows: Figure 1 It is preferable to arrange them scattered in the sea as shown. Figure 1 In the figure, two types of island portions (a first island portion 1 and a second island portion 2) are shown as an example.

[0044] The island-in-the-sea composite polyester fiber of the present invention preferably has an island portion fiber length difference of 15 to 40% after sea removal treatment by alkali treatment and dry heat treatment under the following conditions.

[0045] 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

[0046] If the yarn length difference in the islands after sea removal is 15% or more, the monofilaments are easily pulled out during the napping process, resulting in longer naps, improved bulkiness, and a better nap thickness. If the yarn length difference is 40% or less, a decrease in the hand feel (roughness) caused by overall fabric shrinkage is suppressed, resulting in a high-quality fabric. The yarn length difference in the islands after sea removal is more preferably 20-35%.

[0047] The difference in yarn length between islands was calculated using the following formula (1), with the shortest island length being L1 and the longest island length being L2 among the islands in the fibers after alkali treatment and dry heat treatment. The yarn length was measured under a load of 0.1 g / dtex.

[0048] Wire length difference (%) = (L2-L1) / L1×100···(1)

[0049] Because alkaline dissolution using caustic soda as a dissolving agent is widely practiced industrially, the sea portion of the sea-island composite polyester fiber of the present invention preferably contains polyester as its main component. Furthermore, a copolyester comprising isophthalic acid or a derivative thereof having a metal sulfonate group and polyalkylene glycol is suitable, and a combination of 5-sodium sulfoisophthalate and polyethylene glycol is particularly preferred.

[0050] The content of isophthalic acid having a metal sulfonate group is preferably 5.0 to 15.0 mol%. An isophthalic acid content of 5.0 mol% or greater improves the solubility of the sea portion during sea removal, suppressing fusion between monofilaments caused by undissolved sea components. Furthermore, an isophthalic acid content of 15 mol% or less suppresses polymer softening, improving processability during weaving and knitting.

[0051] The number average molecular weight of the polyalkylene glycol is preferably 500 to 2000. A number average molecular weight of 500 or greater improves the solubility of the sea portion during sea removal treatment, suppressing fusion between filaments caused by the undissolved sea component. Furthermore, since the molecular mobility of the sea component during melt spinning is improved, orientation of the island portion is facilitated, and the orientation parameters of the island portion are appropriately valued, resulting in a significant difference in yarn length and excellent fiber opening and bulkiness, which is preferred. A number average molecular weight of 2000 or less for the polyalkylene glycol improves compatibility with polyester, resulting in excellent spinning properties.

[0052] Furthermore, the polyalkylene glycol content in the polyester polymer is preferably 5.0 to 15.0% by weight. A polyalkylene glycol content of 5.0% or more by weight improves the solubility of the sea portion during sea removal, suppressing fusion between filaments caused by undissolved sea components. Furthermore, since the molecular mobility of the sea component is enhanced during melt spinning, orientation of the island portions is facilitated, and the orientation parameters of the island portions are appropriately determined, resulting in a pronounced difference in yarn length and excellent fiber opening and bulkiness. This is preferable. Even if the polyalkylene glycol content exceeds 15.0% by weight, the effect of improving the solubility of the sea portion reaches its limit.

[0053] Furthermore, when polyester is blended as the sea portion, the intrinsic viscosity (hereinafter referred to as IV) of the sea portion polymer is preferably between 0.50 and 0.75. If the IV is 0.50 or greater, stress on the sea portion increases during spinning, while stress concentration on the island portions is suppressed. Consequently, the orientation parameters of the island portions are appropriately adjusted, suppressing increased shrinkage of the yarn and allowing for the production of high-quality fabrics. On the other hand, if the IV of the sea portion polymer is 0.75 or less, stress concentration on the sea portion is suppressed during spinning, while stress on the island portions increases. Consequently, the orientation parameters of the island portions are appropriately adjusted, resulting in a more pronounced yarn length difference and excellent fiber opening and bulkiness. A more preferred IV of the sea portion polymer is between 0.55 and 0.70.

[0054] Without prejudice to the purpose of the present invention, for each of the sea polymer and the island polymer, the copolymerization components other than the above can be copolymerized with 10 mol% or less. In addition, inorganic particles such as titanium dioxide can be added as a matting agent, and silicon dioxide particles can be added as a lubricant as needed.

[0055] The cross-sectional shape of the island portion of the sea-island composite polyester fiber of the present invention is not particularly limited, and may be, for example, a circular cross-section, a flat cross-section, a lens-shaped cross-section, or other known irregular cross-sections.

[0056] The number of islands in the sea-island composite polyester fiber of the present invention is preferably 12 to 432 islands per monofilament. If the number of islands per monofilament is 12 or more, the island portion can be arranged in the sea portion without gaps, so the morphological stability of the composite fiber becomes higher, which is preferred. In addition, by making the number of islands less than 432 islands per monofilament, the fusion disadvantage of the island portion can be avoided. Furthermore, by reducing the difference in contact time of the island portion in the surface layer and the inner layer of the composite fiber with the solvent when the sea portion is dissolved and removed, the fiber diameter deviation of the fiber obtained from the island portion is small, and high-strength microfibers can be obtained. A further preferred range of the number of islands in the composite fiber is 32 to 192 islands per monofilament.

[0057] In the island-in-the-sea composite polyester fiber of the present invention, the weight proportion of the sea portion is preferably 10-30%. A sea portion content of 10% by weight or more prevents fusion of the island portions, improves the efficiency of the sea removal process, and produces a high-strength, high-quality fabric. Furthermore, a sea portion content of 30% by weight or less is preferred because it shortens the time required to dissolve and remove the sea portion and reduces the amount of polymer dissolved, thereby improving microfiber productivity. A more preferred range for the weight proportion of the sea portion in the island-in-the-sea composite polyester fiber is 15-25%.

[0058] Next, an example of the method for producing the sea-island composite polyester fiber of the present invention will be described in detail.

[0059] The sea-island composite polyester fiber of the present invention can be produced by either a two-step method in which the discharged polymer is temporarily wound as an undrawn yarn, and then stretched to a predetermined breaking elongation using a conventional stretching machine, or a one-step method in which stretching is continued without temporary winding. However, considering the quality stability and production stability in the longitudinal direction of the fiber, production using the direct spinning and stretching method is the most superior.

[0060] The nozzle used for fiber production can use an existing composite spinning nozzle, but it is preferred to use a composite nozzle described in Japanese Patent Application Laid-Open No. 2011-174215, which is a laminate of three major components: a metering plate, a distribution plate, and a discharge plate, because it can stably produce sea-island composite fibers.

[0061] In order to control the orientation parameters of the island portion within such a range, in addition to the selection of the sea portion polymer, the intrinsic viscosity ratio of the island portion polymer and the cooling and solidification conditions can also be preferably controlled.

[0062] The intrinsic viscosity ratio of the polyester flakes in the islands, calculated as the intrinsic viscosity of the high-viscosity component divided by the intrinsic viscosity of the low-viscosity component, is preferably 1.2 to 1.6. When the intrinsic viscosity ratio is 1.2 or greater, the orientation parameter ratio becomes appropriate due to the difference in spinning stress experienced by the different islands, resulting in a yarn with excellent fiber opening and bulkiness due to the difference in yarn length. 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 becomes appropriate, and increased yarn shrinkage is suppressed, resulting in a high-quality fabric.

[0063] In fiber production, in order to control the cooling and solidification of the discharged polymer and to adjust the orientation parameter ratio of different islands to an appropriate value, the distance from the nozzle discharge surface to the cooling surface (cooling start distance) is preferably 250 to 450 mm. The orientation of the islands is easily affected by the viscosity difference during melting. If the cooling start distance is greater than 250 mm, the melting time can be ensured, and the orientation difference between the different island polymers is easily generated, so the orientation parameter ratio falls within the appropriate range. If the cooling start distance is long, the orientation parameter ratio becomes larger, but if the cooling start distance is less than 450 mm, the U% indicating the unevenness of the strands in the longitudinal direction reaches a good value.

[0064] By applying the content of polyalkylene glycol in the sea polymer, the number average molecular weight, the intrinsic viscosity of the sea polymer, the intrinsic viscosity ratio of the island polymer, and the cooling start distance, it is possible to obtain sea island composite polyester fibers that can make the orientation parameters of the island portion appropriate values, express the difference in yarn length due to the difference in thermal shrinkage, improve the fiber opening and bulkiness when making fabrics, and obtain the raising uniformity and raising thickness that cannot be achieved by previous yarns.

[0065] The sea-island composite polyester fiber of the present invention obtained as described above is preferably used for fabrics and clothing. The fabric form can be selected according to the intended purpose, such as woven fabric, knitted fabric, or nonwoven fabric, including clothing. Raising the fabric after production can create a high-quality material like suede. Depending on the intended purpose, the fiber can be suitably used in shirts, blouses, shorts, suits, blouses, shoes, bags, and base fabrics.

[0066] Example

[0067] Hereinafter, the present invention will be described in further detail with reference to examples.

[0068] A. Intrinsic viscosity (IV)

[0069] The intrinsic viscosity of the polymer was calculated from the following formula (2).

[0070] The relative viscosity ηr in formula (2) is determined by dissolving 0.8 g of a sample polymer in 10 mL of O-chlorophenol (OCP) having a purity of 98% or more and using an Ostwald viscometer at 25°C according to the following formula (3).

[0071] Intrinsic viscosity (IV) = 0.0242ηr + 0.2634···(2)

[0072] etar=eta / eta0=(t×d) / (t0×d0)···(3)

[0073] [In formula (3), η is the viscosity of the polymer solution, η0 is the viscosity of the OCP, t is the falling time of the solution (seconds), and d is the density of the solution (g / cm 3 ), t0 is the falling time of OCP (seconds), d0 is the density of OCP (g / cm 3 ). ]

[0074] B. Orientation parameters of the island

[0075] The fiber sample was measured by laser Raman spectroscopy at 1615 cm -1 The intensity of the Raman band derived from the stretching of the carbon-carbon double bond (C=C) of polyethylene terephthalate (PET) in the polarization direction perpendicular to the fiber axis and the intensity of the Raman band at 1730 cm -1 The band intensity ratio is calculated from the band intensity of the Raman band of the stretching of the carbon-oxygen double bond (C=O) of PET confirmed nearby in the polarization direction perpendicular to the fiber axis. The analysis results of the band intensity ratio of the C=C stretching and C=O stretching of the uniaxially stretched PET film in the polarization direction perpendicular to the fiber axis are used as calibration data, and the band intensity ratio is converted into orientation parameters and output.

[0076] Band intensity ratio = I 1615 Vertical / I 1730 vertical

[0077] Orientation parameter = -4.3143 × band intensity ratio + 12.711 (approximate formula for linear correlation using the analysis results of uniaxially stretched PET film as calibration data)

[0078] In addition, the sample for orientation measurement was sliced ​​by a microtome after being embedded in resin (bisphenol epoxy resin, cured for 24 hours). The slice thickness was set to 2.0 μm. The sliced ​​sample was cut slightly obliquely from the fiber axis in such a way that the cut surface became an ellipse, and the position where the thickness of the short axis of the ellipse became a certain thickness was selected for measurement. The measurement was carried out in microscopic mode, and the spot diameter of the laser at the sample position was 1 μm. The orientation measurement was carried out under polarized light conditions. The case where the polarization direction is perpendicular to the fiber axis is set as the vertical condition, and the band intensity ratio is calculated from the respectively obtained Raman band intensities. In addition, each island portion was measured 4 times (n=4), and the average value was calculated. The detailed conditions are shown below.

[0079] (Laser Raman spectroscopy)

[0080] Device; T-64000 (Joobin Yvon / Horiba Co., Ltd.)

[0081] Conditions; Measurement mode; Micro-Raman

[0082] Objective lens: ×100

[0083] Beam diameter: 1μm

[0084] Light source: Ar+ laser / 514.5nm

[0085] Laser power: 50mW

[0086] Diffraction grating; Single 1800gr / mm

[0087] Slit; 100μm

[0088] Detector: CCD / Jobin Yvon 1024×256

[0089] C. Outer diameter of the island

[0090] 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 VHX-2000 microscope manufactured by Keyence Corporation. Five monofilaments were randomly extracted from the resulting photographs. The major diameter of each of the four islands (n = 4) per monofilament was measured, and the arithmetic average of the island diameters of a total of 20 (n = 20) was taken as the average island diameter. In the case of an island with an irregular cross section, the diameter of the circle that contacts the portion that is convex toward the outside of the fiber cross-sectional shape was calculated as the island diameter.

[0091] D. Strength and elongation

[0092] Fiber samples were measured according to JIS L1013-2010 - Tensile Strength and Elongation, and a tensile strength-elongation curve was plotted. The test conditions were a constant-rate elongation tester, a 50 cm gap between the grips, and a tensile speed of 50 cm / minute. In cases where the tensile strength at break was lower than the peak strength, the peak tensile strength and elongation at that time were measured. Strength was calculated using the following formula.

[0093] Elongation = elongation at break (%)

[0094] Strength = tensile strength at break (cN) / fineness (dtex)

[0095] E. Fineness

[0096] The fiber sample was measured for weight per unit length in an atmosphere of 25°C and 55% RH, and the weight equivalent to 10,000 m was calculated from this value. This measurement was repeated 10 times, and the simple average value was rounded off to the nearest decimal point, which was used as the fineness.

[0097] F. Wire length difference

[0098] The yarn length difference is calculated using the following steps (a) to (c).

[0099] (a) Take a 15-20 cm long sea-island composite polyester fiber filament, tie two knots at intervals of about 5 cm and mark them. Then, connect and secure the two ends of the filament to a suitable metal frame of about 10 cm in length.

[0100] (b) The metal frame prepared in item (a) is immersed in a solution in which the sea portion of the easily soluble component can be dissolved to remove the sea portion. In the case where the easily soluble component is a copolyester composed of isophthalic acid or its derivative having a metal sulfonate group and polyalkylene glycol, an aqueous sodium hydroxide solution (concentration 1 g / L) is used as the alkaline aqueous solution. In addition, the alkaline aqueous solution is heated to 92°C and the immersion time is set to 30 minutes. The metal frame is then removed and the filament sample is washed with raw water.

[0101] (c) Heat-treat the filament sample in a dryer at 190°C for 1 minute. After cooling, cut the filament sample along the two knots, separate the single islands with tweezers, and measure each island. The length of the longest island is defined as L2, and the length of the shortest island is defined as L1. The difference in yarn length is calculated using the following formula (1). When measuring the yarn length, a load of 0.1 g / dtex is applied.

[0102] Wire length difference (%) = (L2-L1) / L1×100···(1)

[0103] G. Fabric Evaluation (Suede-like Fabric)

[0104] (a) Raised thickness

[0105] The raised thickness was measured at 5 random locations on the suede-like fabric 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.

[0106] (b) Raising uniformity

[0107] Suede-like fabrics were observed using a VHX-2000 microscope manufactured by Keyence Corporation. Five examiners evaluated the fuzz uniformity and conducted a relative evaluation. The average of the examiners' scores was rounded off to the nearest decimal point. A score of 5 was designated "S," a score of 4 was designated "A," a score of 3 was designated "B," and scores of 1 to 2 were designated "C." S and A scores were considered acceptable for fuzz uniformity.

[0108] <Evaluation Criteria>

[0109] 5 points: Excellent

[0110] 4 points: Slightly excellent

[0111] 3 points: Ordinary

[0112] 2 points: slightly worse

[0113] 1 point: poor

[0114] (c) Soft touch

[0115] Five panelists experienced in hand feel evaluation evaluated the soft touch of suede-like fabrics. The average of the panelists' scores was rounded off to the nearest decimal point, with 5 designated as S, 4 as A, 3 as B, and 1-2 as C. S and A scores were considered acceptable for soft touch.

[0116] <Evaluation Criteria>

[0117] 5 points: Excellent

[0118] 4 points: Slightly excellent

[0119] 3 points: Ordinary

[0120] 2 points: slightly worse

[0121] 1 point: poor

[0122] (d) Dyeability

[0123] Five examiners evaluated the dyeability (dark dyeing) of suede-like fabrics dyed with disperse dyes and conducted a relative evaluation. The average of the examiners' scores was rounded off to the nearest decimal point, with 5 being designated as S, 4 as A, 3 as B, and 1-2 as C. S and A scores were considered acceptable.

[0124] (Dyeing conditions)

[0125] Dye; Dinanix Navy S-2G 200% 0.3% owf

[0126] Dyeing auxiliary; Tetrosin PEC 5.0% owf

[0127] SunSalt 1.0% owf

[0128] Bath ratio: 1:100

[0129] Dyeing: After treating at 50°C for 15 minutes, the temperature was increased at a rate of 1.6°C / min and treated at 98°C for 20 minutes.

[0130] <Evaluation Criteria>

[0131] 5 points: Overall dark dyeing, very excellent

[0132] 4 points: Slightly excellent

[0133] 3 points: Ordinary

[0134] 2 points: slightly worse

[0135] 1 point: lightly dyed overall, poor

[0136] [Example 1]

[0137] (Manufacturing of sea-island composite polyester fibers)

[0138] As the island A polymer for forming the islands A, a copolymerized polyethylene terephthalate (PET1) with an IV of 0.67 was prepared by copolymerizing 7.1 mol% of isophthalic acid and 4.4 mol% of a bisphenol A ethylene oxide adduct relative to the total acid components. As the island B polymer for forming the islands B, a polyethylene terephthalate (PET2) with an IV of 0.51 was prepared, with an intrinsic viscosity ratio of 1.31. As the readily soluble sea polymer, a readily alkali-soluble polyethylene terephthalate (PET1) with an IV of 0.69 was prepared, comprising 8.0 mol% of 5-sodium sulfoisophthalate and 9.0 wt% of polyethylene glycol with a number average molecular weight of 1000.

[0139] The island A polymer, island B polymer and sea polymer are melted at 265°C, 280°C and 280°C respectively using an extruder, and then metered by a pump to a spinning temperature of 275°C, and flowed into the nozzle while maintaining the temperature. The weight composite ratio of island A, island B and sea is set to 40 / 40 / 20, and flows into a sea-island composite spinneret with 48 islands (island A = 24 islands, island B = 24 islands) and 24 holes. Each polymer merges inside the nozzle, and the sea polymer contains the island polymer (island A polymer, island B polymer), forming Figure 1 A composite structure with islands A (the first island indicated by reference numeral 1) and islands B (the second island indicated by reference numeral 2) dispersed therein was discharged from a nozzle. The discharged filaments were cooled and solidified by passing through an air cooling device with a cooling start distance of 330 mm. An oil solution was then applied, and the filaments were taken up at a speed of 1200 m / min using rollers heated to 90°C. They were stretched at a ratio of 3.3 times, heat-set using rollers heated at 150°C, and then wound up using a winder at a speed of 3950 m / min to produce 70 dtex-12 f (filament) island-in-the-sea composite polyester fibers. The evaluation results of the resulting island-in-the-sea composite polyester fibers are shown in Table 1.

[0140] (Manufacture of suede-like fabrics)

[0141] The sea-island composite polyester fiber was then twisted in the S direction at 800 T / m using a two-for-one twisting machine. The yarn was then steamed at 75°C for 30 minutes to set the twist and shape for warping. The weft yarn consisted of a 56 dtex, 24f polytrimethylene terephthalate (PTT) / PET bifilament.

[0142] Using these warp and weft yarns, a 5-piece satin weave was woven using an air jet loom at a grey fabric density (warp: 222 strands / inch, weft: 97 strands / inch). Next, the resulting woven fabric was subjected to open-width continuous scouring at 98°C, liquid flow relaxation treatment was performed at 130°C, and intermediate setting was performed at 180°C. Then, it was immersed in an aqueous sodium hydroxide solution (1 g / L) and desealing was performed. The resulting fabric was subjected to a raising process with a card cloth raising machine and then fine setting was performed at 160°C to obtain a suede-like fabric. The results of the evaluation of the resulting suede-like fabric are shown in Table 1.

[0143] [Example 2]

[0144] A suede-like fabric was obtained by the same method as in Example 1, except that the nozzle was changed so that the number of islands per monofilament was 108 (island portion A = 54 islands, island portion B = 54 islands). The evaluation results are shown in Table 1.

[0145] [Example 3]

[0146] A suede-like fabric was obtained by the same method as in Example 1, except that the nozzle was changed so that the number of islands per monofilament was 22 (Island A = 11 islands, Island B = 11 islands). The evaluation results are shown in Table 1.

[0147] [Example 4]

[0148] A suede-like fabric was obtained by the same method as in Example 1, except that the nozzle was changed so that the number of islands per monofilament was 432 (island portion A = 216 islands, island portion B = 216 islands). The evaluation results are shown in Table 1.

[0149] [Example 5]

[0150] A suede-like fabric was obtained by the same method as in Example 1, except that the nozzle was changed so that the number of islands per monofilament was 12 (island portion A = 6 islands, island portion B = 6 islands). The evaluation results are shown in Table 1.

[0151] [Example 6]

[0152] A suede-like fabric was obtained by the same method as in Example 1, except that polyethylene terephthalate (PET3) with an IV of 0.56 was prepared as the island B polymer for forming the island B, and the intrinsic viscosity ratio was adjusted to 1.20. The results are shown in Table 1.

[0153] [Example 7]

[0154] As the island A polymer for forming the island A, a polyethylene terephthalate (PET4) having an IV = 0.82 and copolymerized with 7.1 mol% of isophthalic acid and 4.4 mol% of a bisphenol A ethylene oxide adduct relative to the total acid components was prepared to achieve an intrinsic viscosity ratio of 1.60. A suede-like fabric was obtained by the same method as in Example 1, except that the above-described method was used. A 70 dtex, 12 f sea-island composite polyester fiber was obtained. The evaluation results are shown in Table 1.

[0155] [Example 8]

[0156] A readily alkali-soluble polyethylene terephthalate (PET2) with an IV of 0.50 (easily soluble PET2) containing 8.0 mol% of 5-sodium sulfoisophthalate and 9.0 wt% of polyethylene glycol with a number average molecular weight of 1000 was prepared as a readily soluble sea polymer. A suede-like fabric was obtained by the same method as in Example 1, except that the following procedures were followed: 70 dtex, 12 f sea-island composite polyester fiber was obtained. The evaluation results are shown in Table 2.

[0157] [Example 9]

[0158] As a readily soluble sea polymer, a readily alkali-soluble polyethylene terephthalate (PET3) having an IV of 0.75 (easily soluble PET3) was prepared, comprising 8.0 mol% of 5-sodium sulfoisophthalate and 9.0 wt% of polyethylene glycol having a number average molecular weight of 1000. A suede-like fabric was obtained by the same method as in Example 1, except that the following was used: 70 dtex, 12 f sea-island composite polyester fiber was obtained. The evaluation results are shown in Table 2.

[0159] [Example 10]

[0160] As the readily soluble sea polymer, a readily alkali-soluble polyethylene terephthalate (PET4) with an IV of 0.69 (easily soluble PET4) containing 8.0 mol% of 5-sodium sulfoisophthalate and 9.0 wt% of polyethylene glycol with a number average molecular weight of 500 was prepared. A suede-like fabric was obtained by the same method as in Example 1, except that the above-mentioned components were copolymerized to obtain a 70 dtex, 12f sea-island composite polyester fiber. The evaluation results are shown in Table 2.

[0161] [Example 11]

[0162] As the readily soluble sea polymer, a readily alkali-soluble polyethylene terephthalate (PET5) having an IV of 0.69 (easily soluble PET5) was prepared, comprising 8.0 mol% of 5-sodium sulfoisophthalate and 9.0 wt% of polyethylene glycol with a number average molecular weight of 2000. A suede-like fabric was obtained by the same method as in Example 1, except that the following was not included: a 70 dtex, 12 f sea-island composite polyester fiber was obtained. The evaluation results are shown in Table 2.

[0163] [Example 12]

[0164] As the readily soluble sea polymer, a readily alkali-soluble polyethylene terephthalate (PET6) with an IV of 0.69 (comprising 8.0 mol% of 5-sodium sulfoisophthalate and 5.0 wt% of polyethylene glycol having a number average molecular weight of 1000) was prepared. A suede-like fabric was obtained by the same method as in Example 1, except that the readily soluble sea polymer was copolymerized to produce 70 dtex, 12 f sea-island composite polyester fibers. The evaluation results are shown in Table 2.

[0165] [Example 13]

[0166] As the readily soluble sea polymer, a readily alkali-soluble polyethylene terephthalate (PET7) with an IV of 0.69 (easily soluble) containing 8.0 mol% of 5-sodium sulfoisophthalate and 15.0 wt% of polyethylene glycol with a number average molecular weight of 1000 was prepared. A suede-like fabric was obtained by the same method as in Example 1, except that the following procedures were followed: 70 dtex, 12 f sea-island composite polyester fiber was obtained. The evaluation results are shown in Table 2.

[0167]

[0168]

[0169] [Comparative Example 1]

[0170] Except for changing the nozzle so that the number of islands per monofilament was 720 (island portion A = 360 islands, island portion B = 360 islands), the same method as in Example 1 was used to obtain a 70 dtex, 12f sea-island composite polyester fiber and a suede-like fabric. The evaluation results are shown in Table 3.

[0171] Since the outer diameter of the sea-island composite polyester fiber of Comparative Example 1 was as small as 0.8 μm after the sea was removed, the suede-like fabric was lightly dyed as a whole and had poor dyeability.

[0172] [Comparative Example 2]

[0173] A suede-like fabric was obtained by the same method as in Example 1, except that the nozzle was changed so that the number of islands per monofilament became 8 (island portion A = 4 islands, island portion B = 4 islands). The evaluation results are shown in Table 3.

[0174] Since the outer diameter of the sea-island composite polyester fiber of Comparative Example 2 was as large as 7.5 μm after the sea was removed, the suede-like fabric had a hard feel and poor soft touch.

[0175] [Comparative Example 3]

[0176] A suede-like fabric was obtained by the same method as in Example 1, except that polyethylene terephthalate (PET5) with an IV of 0.60 was prepared as the island B polymer for forming the island B, and the intrinsic viscosity ratio was adjusted to 1.12. The evaluation results are shown in Table 3.

[0177] The island-in-the-sea composite polyester fiber of Comparative Example 3 has low orientation parameter of the maximum orientation component and the ratio of the orientation parameter of the maximum orientation component to the orientation parameter of the minimum orientation component (orientation parameter ratio), and small difference in yarn length. Therefore, the raised thickness and raised uniformity of the suede-like fabric are poor.

[0178] [Comparative Example 4]

[0179] As the island A polymer for forming the island A, a polyethylene terephthalate (PET6) having an IV = 0.90 was prepared by copolymerizing 7.1 mol% of isophthalic acid and 4.4 mol% of a bisphenol A ethylene oxide adduct with respect to the total acid components to achieve an intrinsic viscosity ratio of 1.76. A suede-like fabric was obtained by the same method as in Example 1, except that the above-described method was used. A 70 dtex, 12 f sea-island composite polyester fiber was obtained. The evaluation results are shown in Table 3.

[0180] The island-in-the-sea composite polyester fiber of Comparative Example 4 had high orientation parameters and high orientation parameter ratios of the maximum orientation component, resulting in excessive yarn shrinkage. As a result, the suede-like fabric had a hard feel and poor soft touch.

[0181] [Comparative Example 5]

[0182] As a readily soluble sea polymer, a readily alkali-soluble polyethylene terephthalate (V = 0.40) (easily soluble PET8) containing 8.0 mol% of 5-sodium sulfoisophthalate and 9.0 wt% of polyethylene glycol with a number average molecular weight of 1000 was prepared. A suede-like fabric was obtained by the same method as in Example 1, except that the following was used: 70 dtex, 12 f sea-island composite polyester fiber was obtained. The evaluation results are shown in Table 3.

[0183] The island-in-the-sea composite polyester fiber of Comparative Example 5 had high orientation parameters and orientation parameter ratios of the maximum orientation component, resulting in excessive yarn shrinkage. As a result, the suede-like fabric had a hard feel and poor soft touch.

[0184] [Comparative Example 6]

[0185] As the readily soluble sea polymer, a readily alkali-soluble polyethylene terephthalate (V = 0.80) (easily soluble PET9) containing 8.0 mol% of 5-sodium sulfoisophthalate and 9.0 wt% of polyethylene glycol with a number average molecular weight of 1000 was prepared. A suede-like fabric was obtained by the same method as in Example 1, except that the following was used: 70 dtex, 12 f sea-island composite polyester fiber. The evaluation results are shown in Table 3.

[0186] The island-in-the-sea composite polyester fiber of Comparative Example 6 had a low orientation parameter of the maximum orientation component and a small difference in yarn length, so the raised thickness and raised uniformity of the suede-like fabric were poor.

[0187] [Comparative Example 7]

[0188] As the readily soluble sea polymer, a readily alkali-soluble polyethylene terephthalate (PET10) having an IV of 0.69 (easily soluble) was prepared, comprising 8.0 mol% of 5-sodium sulfoisophthalate and 9.0 wt% of polyethylene glycol having a number average molecular weight of 4000. A suede-like fabric was obtained by the same method as in Example 1, except that the copolymerization was performed such that 8.0 mol% of 5-sodium sulfoisophthalate and 9.0 wt% of polyethylene glycol having a number average molecular weight of 4000 was used. The results of the evaluation are shown in Table 3.

[0189] The island-in-the-sea composite polyester fiber of Comparative Example 7 had a low orientation parameter of the maximum orientation component and a small difference in yarn length, resulting in poor nap thickness and uniformity in the suede-like fabric. Furthermore, the yarn strength was low, resulting in poor durability of the suede-like fabric.

[0190] [Comparative Example 8]

[0191] As a readily soluble sea polymer, a readily alkali-soluble polyethylene terephthalate (PET11) having an IV of 0.69 (easily soluble) was prepared, comprising 8.0 mol% of 5-sodium sulfoisophthalate and 3.0 wt% of polyethylene glycol having a number average molecular weight of 1000. A suede-like fabric was obtained by the same method as in Example 1, except that the following was used: 70 dtex, 12 f sea-island composite polyester fiber was obtained. The evaluation results are shown in Table 3.

[0192] The island-in-the-sea composite polyester fiber of Comparative Example 8 had a low orientation parameter of the maximum orientation component and a small difference in yarn length, so the raised thickness and raised uniformity of the suede-like fabric were poor.

[0193] [Comparative Example 9]

[0194] A 70 dtex, 12f sea-island composite polyester fiber was obtained by the same method as in Example 1, except that a readily soluble sea polymer was prepared, containing a component copolymerized to 5.0 mol% of 5-sodium sulfoisophthalate, and having an IV of 0.55 (easily soluble PET12). This fiber was then used to produce a suede-like fabric. The evaluation results are shown in Table 3.

[0195] The island-in-the-sea composite polyester fiber of Comparative Example 9 had low orientation parameters and orientation parameter ratios of the maximum orientation component and small yarn length difference, resulting in poor nap thickness and uniformity in the suede-like fabric. Furthermore, the yarn strength was low, resulting in poor durability of the suede-like fabric.

[0196] [Comparative Example 10]

[0197] The same method as in Example 1 was used except that the cooling start distance of the yarn discharged from the nozzle was changed to 200 mm to obtain a sea-island composite polyester fiber of 70 dtex and 12 f, thereby obtaining a suede-like fabric.

[0198] The island-in-the-sea composite polyester fiber of Comparative Example 10 had a low orientation parameter of the maximum orientation component and a small difference in yarn length, so the raised thickness and raised uniformity of the suede-like fabric were poor.

[0199]

[0200] Although the present invention has been described in detail using a specific scheme, it is obvious to those skilled in the art that various changes and modifications can be made without departing from the intention and scope of the present invention. In addition, this application is based on Japanese patent application (Special Application No. 2020-193153) filed on November 20, 2020, which is incorporated by reference in its entirety.

[0201] Explanation of symbols

[0202] 1: Island 1 (Island A)

[0203] 2: The second island (island B).

Claims

1. A sea-island composite polyester fiber having a sea-island structure, wherein the sea-island structure comprises a sea portion and two or more different island portions, wherein the outer diameter of the island portion is 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 in the island portion, i.e., the 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. The sea portion comprises a copolyester obtained by copolymerizing isophthalic acid or a derivative thereof having a metal sulfonate group with polyalkylene glycol, wherein the number average molecular weight of the polyalkylene glycol is 500 to 2000. The intrinsic viscosity of the seawater polymer represented by the following formula (2) is 0.50 to 0.

75. Intrinsic viscosity (IV) = 0.0242ηr + 0.2634 Formula (2) The relative viscosity ηr in formula (2) is determined by dissolving 0.8 g of a sample polymer in 10 mL of o-chlorophenol (OCP) having a purity of 98% or more and using an Ostwald viscometer at 25°C using the following formula (3): etar=eta / eta0=(t×d) / (t0×d0) Formula (3) In formula (3), η is the viscosity of the polymer solution, η0 is the viscosity of the OCP, t is the falling time of the solution, d is the density of the solution, t0 is the falling time of the OCP, and d0 is the density of the OCP. The unit of falling time is seconds, and the unit of density is g / cm 3 , And, the orientation parameter is determined as follows: The fiber sample was measured by laser Raman spectroscopy at 1615 cm -1 The intensity of the Raman band at 1730 cm-1 derived from the stretching of the carbon-carbon double bond (C=C) of polyethylene terephthalate (PET) in the polarization direction perpendicular to the fiber axis is also observed. -1 The band intensity ratio is calculated from the band intensity of the Raman band of stretching of the carbon-oxygen double bond (C=O) of PET confirmed nearby in the polarization direction perpendicular to the fiber axis. The band intensity ratio is converted into an orientation parameter and output using the analysis results of the band intensity ratio of the C=C stretching and C=O stretching of the uniaxially stretched PET film in the polarization direction perpendicular to the fiber axis as calibration data. Band intensity ratio = I 1615 Vertical / I 1730 vertical Orientation parameter = -4.3143 x band intensity ratio + 12.

711.

2. The sea-island composite polyester fiber according to claim 1, wherein the difference in fiber length of the island portion represented by the following formula (1) is 15 to 40% after the sea-island composite polyester fiber is subjected to an alkali treatment and a dry heat treatment under the following conditions. Alkali treatment conditions: 1g / L sodium hydroxide aqueous solution, 92°C, 30 minutes, no load Dry heat treatment conditions: 190°C, 1 minute, no load Wire length difference (%) = (L2-L1) / L1×100……(1) In the formula (1), L1 is the length of the shortest island portion, and L2 is the length of the longest island portion.

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