Highly irregular cross-section polypropylene fiber

Abstract

To provide a polypropylene fiber that is bulky, has excellent texture and can be suitably adopted as a fiber structure.SOLUTION: A polypropylene fiber is characterized by having a modification degree M value of 1.2 to 3.0 in the fiber cross section.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to polypropylene fibers. [Background technology]

[0002] Polypropylene, a type of polyolefin, has a low specific gravity among general-purpose resins, relatively high strength, and excellent chemical resistance. Its excellent moldability, such as its ability to be easily molded using a standard melt extruder, has led to its use in a wide range of applications, from automotive parts to home appliances, stationery, and even medical materials. These excellent properties are also utilized in textile products, such as hygiene products like masks and diapers, interior applications like tile carpets, household rugs, and car mats, and materials like ropes, protective netting, filter cloths, narrow tapes, braided cords, and upholstery. However, there are few examples of its use in clothing.

[0003] This is because polypropylene fibers have no polar functional groups and are difficult to dye, which is a problem in clothing.

[0004] On the other hand, in light of the functionality of polypropylene fibers such as light weight and water repellency, efforts have been made to try to color the fibers in order to enable their use in clothing. As a proposal for coloring by adding pigments or dyeable polymers, Patent Document 1 discloses a technology relating to dyeable polypropylene fibers, which are polymer alloy fibers obtained by blending a copolymer polyester copolymerized with cyclohexanedicarboxylic acid, a dyeable polymer, with polypropylene in order to impart vivid and deep color development.

[0005] With the proposal of technology that ensures color development for clothing textiles, such as that in Patent Document 1, polypropylene fibers can now be used in clothing, and it is expected that they will be used as comfortable clothing fibers by further improving the polymer properties. Possible ways to improve polypropylene fibers by utilizing their polymer properties include, for example, improving texture, bulkiness, lightness, and water repellency by creating modified cross sections.

[0006] Regarding the advancement of fibers by forming them into modified cross sections, Patent Document 2 discloses a technology for forming modified fiber cross sections and controlling the microvoids contained therein in order to improve texture, bulkiness, light weight, whiteness, light blocking properties, and heat retention, and further to maintain the manufacturing processability and durability of products even if the fibers have microvoids.

[0007] Patent Document 3 discloses a technique for producing a hollow irregular cross section that has sufficient crimpability, excellent bulk, light weight, and heat retention, and does not collapse, by forming an irregular cross section consisting of a core portion having a hollow and a fin portion, and by generating crimp by anisotropic cooling. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2017 / 154665 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-161218 [Patent Document 3] Japanese Patent Publication No. 2020-70530 Summary of the Invention [Problem to be solved by the invention]

[0009] Attempts to improve the tactile feel and functionality of fibers by forming a modified cross section have been disclosed for a relatively long time, but most of these efforts have focused on synthetic fibers used in clothing, such as polyester and polyamide, and no examples of polypropylene fibers have been successfully formed with a modified cross section. This is because polypropylene has polymer properties such as a very high specific heat and a low melting point and glass transition temperature. Specifically, to form a modified cross section fiber, the fiber must be rapidly cooled to its solidification point after being discharged from a spinneret equipped with modified holes, and solidified while maintaining a highly modified cross section. However, due to the thermal characteristics described above, polypropylene takes a long time to solidify as a fiber after being discharged from the spinneret, compared to polymers that solidify relatively quickly, such as polyester and polyamide. Furthermore, the strong surface tension acting from the molten to semi-molten state significantly reduces the degree of fiber modification, making it difficult to form a highly modified cross section polypropylene fiber.

[0010] For this reason, Patent Document 1 achieves dyeable polypropylene fibers that ensure color development after dyeing by blending easily dyeable components with polypropylene fibers to which dyes are not fixed, but does not include a technical idea that claims functionality through irregular cross-sections, and does not disclose any means for achieving this.

[0011] Furthermore, Patent Documents 2 and 3 disclose that, in polyester or polyester-based fibers, fibers having a modified cross section or hollow modified cross section have been achieved by drilling slit holes of a fixed width in the modified discharge holes of a spinneret. However, Patent Documents 2 and 3 also do not disclose any description regarding the highly modified cross section of polypropylene fibers or the means for achieving this. Furthermore, they do not disclose any description regarding the improvement in functionality or technical concept achieved by the highly modified cross section of polypropylene fibers.

[0012] As described above, there is a demand for polypropylene fibers that can be dyed and have the advanced functionality required for clothing. Therefore, an object of the present invention is to provide a highly modified cross-section polypropylene fiber that solves the technical problems related to polypropylene fibers described above and can be used in a wide range of fiber materials, from clothing to industrial materials. [Means for solving the problem]

[0013] The above problem is solved by the fiber cross section, where the irregularity M value is 1.2 to 3.0. It has five or more protrusions that protrude radially from the center of the fiber cross section, and the protrusion shape a / b is 1.5 or more and 3.0 or less. The above-mentioned problems can be solved by a polypropylene fiber characterized by the above-mentioned. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide polypropylene fibers that have not only bulkiness and lightness not found in conventional fibers but also high water repellency specific to polypropylene, and by forming the fibers into a modified cross section, long-term high water repellency is exhibited due to the lotus effect, and that have excellent texture and can be suitably used as fiber structures. When made into a fiber structure, the polypropylene fibers obtained by the present invention can be suitably used in applications requiring excellent lightness and water repellency. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram showing an example of the cross-sectional shape of a polypropylene fiber of the present invention having no hollow portion. [Figure 2] FIG. 2 is a diagram showing an example of the cross-sectional shape of a polypropylene fiber of the present invention when the fiber has a hollow portion. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention is directed to a polypropylene fiber having a degree of deformation M value of 1.2 to 3.0 in the fiber cross section. The polypropylene fiber of the present invention may be composed solely of polypropylene, as long as it is mainly composed of polypropylene, or may be a polymer alloy fiber composed of a plurality of components further containing other thermoplastic resins.

[0017] The polypropylene of the present invention may be a propylene homopolymer or a copolymer with other α-olefins. One or more other α-olefins (hereinafter sometimes simply referred to as α-olefins) may be copolymerized.

[0018] The α-olefin preferably has 2 to 20 carbon atoms, and the molecular chain of the α-olefin may be linear or branched. Specific examples of the α-olefin include, but are not limited to, ethylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, and 3-ethyl-1-hexene.

[0019] The copolymerization rate of the α-olefin is preferably 20 mol % or less, since a polypropylene fiber having good mechanical properties and heat resistance can be obtained if the copolymerization rate of the α-olefin is 20 mol % or less.

[0020] The polymer alloy fiber of the present invention refers to a fiber in which island components are discontinuously dispersed. Here, "discontinuous island components" means that the island components are present with an appropriate length in the longitudinal direction of the fiber, with the length ranging from several tens of nanometers to several hundreds of thousands of nanometers, and that the shapes of the sea-island structures in two cross sections perpendicular to the fiber axis, i.e., the fiber cross section, observed at any interval within the same single fiber, are different. The discontinuity of the island components in the present invention can be confirmed by the method described in the Examples. When the island components are present in a discontinuously dispersed state, the specific interfacial area of ​​the sea-island interface can be sufficiently increased, thereby suppressing interfacial delamination and resulting in a polymer alloy fiber with excellent mechanical properties and abrasion resistance. Furthermore, because interfacial delamination is suppressed, when dyed, the decrease in color development due to the increase in scattered light caused by interfacial delamination can be suppressed, resulting in a vivid and deep color. As described above, the polymer alloy fiber of the present invention is essentially different from a sea-island composite fiber in which one or more islands are formed continuously and uniformly in the fiber axis direction. Such polymer alloy fibers can be obtained, for example, by molding a polymer alloy composition formed by kneading polypropylene and a thermoplastic resin at any stage before the completion of melt spinning.

[0021] In the polymer alloy fiber of the present invention, polypropylene, which is the main component, is the sea component. Examples of island components include, but are not limited to, polyester, polyamide, and polyolefin. To improve the color development of the polypropylene fiber of the present invention, a dyeable polymer is used as the island component. It is preferable to use polyester as the island component, and it is particularly preferable to use copolymerized polyester.

[0022] In order to improve the color development property, it is possible to reduce the crystallinity of the copolymerized polyester or reduce the refractive index of the copolymerized polyester, but reducing the refractive index of the copolymerized polyester can provide a greater effect.

[0023] Since dyes are less likely to be absorbed into crystalline portions and more likely to be absorbed into amorphous portions, the lower the crystallinity of the copolymerized polyester, the more preferable it is, and amorphous polyester is more preferable, in order to improve color development.

[0024] Furthermore, when the refractive index of the copolymer polyester is reduced, the amount of light reflected from the surface of the copolymer polyester is reduced, allowing light to penetrate sufficiently into the interior of the copolymer polyester, thereby imparting vivid and deep color development. In order to reduce the refractive index of the copolymer polyester, it is effective to reduce the aromatic ring concentration of the copolymer polyester.

[0025] The copolymer polyester of the present invention preferably contains terephthalic acid and ethylene glycol as main components and has a copolymerization component, such as aromatic dicarboxylic acids, such as phthalic acid, isophthalic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 5-sodium sulfoisophthalic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,2'-biphenyldicarboxylic acid, 3,3'-biphenyldicarboxylic acid, 4,4'-biphenyldicarboxylic acid, and anthracenedicarboxylic acid, malonic acid, fumaric acid, maleic acid, succinic acid, itaconic acid, adipic acid, azelaic acid, sebacic acid, 1,11-undecanedicarboxylic acid, and 1,12 Examples of copolymerizable diol components include aromatic diols such as catechol, naphthalene diol, and bisphenol, and aliphatic diols such as trimethylene glycol, tetramethylene glycol, hexamethylene glycol, diethylene glycol, polyethylene glycol, polypropylene glycol, neopentyl glycol, and cyclohexanedimethanol. These copolymerizable components may be used alone or in combination of two or more.

[0026] The polymer alloy fiber of the present invention preferably contains 5.0 to 20.0 parts by weight of copolymerized polyester per 100 parts by weight of the total fiber composition. A copolymerized polyester content of 5.0 parts by weight or more is preferred because dyeing the island components present in large numbers relative to the sea component improves the coloring efficiency of light transmitted through the island components, resulting in vivid, deep color development. On the other hand, a copolymerized polyester content of 20.0 parts by weight or less allows the copolymerized polyester, which has a low refractive index and high color development, to be dispersed in the polypropylene, which has a low refractive index, thereby achieving vivid, deep color development. In addition, this is preferred because it does not impair the light weight, level dyeing ability, or quality of polypropylene.

[0027] In the polymer alloy fiber of the present invention, a compatibilizer may be added as needed to improve the dispersibility of the island components in the polypropylene sea component, control the dispersion state, and improve the interfacial adhesion between the polypropylene sea component and the island components. Furthermore, when forming an island-sea structure by melt spinning, a bulge called "balus" tends to occur just below the spinneret, making the thinning deformation of the fiber unstable. Therefore, a compatibilizer may be used to improve spinning operability by suppressing yarn breakage associated with this balus, and to obtain high-quality fibers with small fineness unevenness and excellent uniformity in the fiber longitudinal direction.

[0028] The compatibilizer in the present invention can be appropriately selected depending on the composition of the sea component polypropylene and the island component, the composite ratio of the sea component polypropylene and the island component, etc. Only one type of compatibilizer may be used, or two or more types may be used in combination.

[0029] When a compatibilizer is added, the polypropylene fiber of the present invention preferably contains 0.1 to 10.0 parts by weight of the compatibilizer per 100 parts by weight of the total composition. A content of 0.1 part by weight or more of the compatibilizer is preferred because it provides a compatibilizing effect between the polypropylene sea component and the island component fibers, thereby reducing the dispersion diameter of the island component fibers and suppressing the aggregation of the dye compound, thereby achieving a monodisperse state. This improves color development efficiency and produces vivid, deep colors, which is preferable. It also improves spinning operability, such as suppressing yarn breakage, and allows the production of high-quality fibers with small fineness variations and excellent uniformity in the fiber longitudinal direction. On the other hand, a content of 10.0 parts by weight or less of the compatibilizer is preferred because it maintains the fiber properties, appearance, and texture derived from the polypropylene sea component and island component fibers that constitute the polypropylene fiber. It is also preferred because it prevents instability in spinning operability caused by an excessive amount of the compatibilizer.

[0030] The polypropylene fiber of the present invention has a non-circularity M value of 1.2 to 3.0 in a cross section perpendicular to the fiber axis, i.e., in the fiber cross section. The non-circular cross section may be symmetric, such as line symmetric or point symmetric, or asymmetric, but is preferably symmetric in order to obtain uniform fiber properties. The non-circularity M value is the ratio (r1 / r2) of the diameter r1 of the circumscribing circle R1 to the diameter r2 of the inscribing circle R2 in the single fiber cross section. The circumscribing circle R1 is the perfect circle with the smallest diameter among the perfect circles that touch at least two points on the outer periphery of the single fiber cross section and do not pass inside the outer periphery of the single fiber cross section. The inscribing circle R2 is the perfect circle with the largest diameter among the perfect circles that are inside the outer periphery of the single fiber cross section and do not pass outside the outer periphery of the single fiber cross section. As long as this inscribing circle R2 is inside the outer periphery of the single fiber cross section and does not pass outside the outer periphery of the single fiber cross section, it may pass through a hollow portion in the single fiber cross section. If the irregularity M value is 1.2 or more, sufficient voids can be formed between the individual fibers, resulting in increased bulk. Furthermore, the presence of sufficient voids improves water repellency due to the lotus effect. An irregularity M value of 1.5 or more is preferable because it further improves water repellency. On the other hand, if the irregularity M value is 3.0 or less, the change in irregularity when friction is applied is small, bulkiness and water repellency are maintained, and fiber strength and processability are also improved. An irregularity M value of 2.0 or less is preferable because it not only provides excellent water repellency but also maintains abrasion resistance.

[0031] The polypropylene fiber of the present invention preferably has protrusions that protrude radially from the center of the fiber cross section, and the protrusions have a cross-sectional shape in which the protrusion shape a / b is 1.5 or more and 3.0 or less. a is the maximum length of the base where the protrusions touch the inscribed circle R2 in the cross section of a single fiber. b is the width of the protrusions when a straight line parallel to the base is drawn to the center of a perpendicular line drawn from the vertex where the protrusions touch the circumscribed circle R1 to the base having the maximum length where the protrusions touch the inscribed circle R2. A protrusion shape a / b of 1.5 or more is preferable because sufficient voids can be formed between the protrusions, resulting in increased bulk. Having sufficient voids also improves water repellency due to the lotus effect. On the other hand, a protrusion shape a / b of 3.0 or less is preferable because the probability of the protrusions penetrating the voids between the protrusions of other single fibers is reduced, thereby preventing a decrease in bulkiness. Furthermore, deformation and peeling of the protrusions when friction is applied are suppressed, thereby maintaining bulkiness and water repellency. It is more preferable that the projection shape a / b is 2.0 or less. Furthermore, it is preferable that the cross-sectional shape of the projections has a / c of ​​0.5 or more and 3.0 or less. c is the length of the perpendicular line drawn from the vertex where the projections touch the circumscribed circle R1 to the base of the longest length where the projections touch the inscribed circle R2. A projection shape a / c of ​​0.5 or more is preferable because it suppresses deformation and peeling of the projections when friction is applied, and maintains bulkiness and water repellency. On the other hand, a projection shape a / c of ​​3.0 or less is preferable because it allows for sufficient voids to be formed between the projections, resulting in bulkiness, and having sufficient voids also improves water repellency due to the lotus effect.

[0032] When the polypropylene fiber of the present invention has a plurality of protrusions protruding radially from the center of the fiber cross section, it is preferable that the protrusions have the same shape and are equally spaced around the periphery of the fiber cross section, since having protrusions of the same shape and being equally spaced results in a symmetrical cross section and makes it possible to obtain uniform fiber properties.

[0033] The polypropylene fiber of the present invention preferably has five or more protrusions protruding radially from the center of the fiber cross section. Four or fewer protrusions, when the spacing between the protrusions is wide, form flat areas on the fiber surface, increasing the surface area in contact with water compared to a round cross section fiber without protrusions, which has a curved surface, reducing the amount of air layer formation and decreasing water repellency, which is undesirable. Furthermore, the increased number of flat areas on the fiber surface allows single fibers to be arranged closer to each other, which also reduces bulkiness, which is undesirable. Having five or more protrusions is preferable because the spacing between protrusions present in the same single fiber is sufficiently narrow, preventing protrusions from other single fibers from penetrating and reducing bulkiness. Furthermore, no flat areas are formed on the single fiber surface, making it difficult for water droplets to enter the spaces between the protrusions when dropped, which increases the amount of air layer formation and improves water repellency, which is preferable.

[0034] The polypropylene fiber of the present invention preferably has at least one hollow portion, and the hollow portion preferably has a hollow ratio of 10% to 50%. A hollow ratio of 10% or more is preferable because it exhibits light weight and bulkiness and is lighter than solid fibers. Furthermore, a hollow ratio of 50% or less is preferable because it prevents deterioration of spinnability, deterioration of fiber properties, and deterioration of abrasion resistance.

[0035] The polypropylene fiber of the present invention preferably contains an antioxidant, which is preferable because it not only inhibits oxidative decomposition of polypropylene due to long-term storage or tumble drying, but also improves the durability of fiber properties such as mechanical properties.

[0036] The antioxidant in the present invention is preferably any one of a phenolic compound, a phosphorus compound, a sulfur compound, and a hindered amine compound. These antioxidants may be used alone or in combination of two or more.

[0037] The polypropylene fiber of the present invention is not particularly limited with respect to the form of the fiber, and may be in any form such as monofilament, multifilament, staple, etc., but is preferably in the form of multifilament or staple in order to take advantage of the properties such as bulkiness due to the modified cross section.

[0038] The single fiber fineness of the polypropylene fiber of the present invention is not particularly limited and can be appropriately selected depending on the application and required properties, but is preferably 0.5 to 20 dtex. The single fiber fineness in the present invention refers to the value obtained by dividing the fineness measured by the method described in the Examples by the number of single fibers. If the single fiber fineness of the polypropylene fiber is 0.5 dtex or more, there is less yarn breakage, and the processability is good, and in addition, there is less generation of fluff during use and excellent durability, so this is preferable. On the other hand, if the single fiber fineness of the polypropylene fiber is 20 dtex or less, the flexibility of the fiber and the fiber structure is not impaired, so this is preferable. The fineness of the polypropylene fiber of the present invention as a multifilament is not particularly limited and can be appropriately selected depending on the application and required properties, but is preferably 10 to 3000 dtex. The fineness in the present invention refers to the value measured by the method described in the Examples. Polypropylene fibers having a fineness of 10 dtex or more are preferred because they have less yarn breakage, good processability, less fuzz generation during use, and excellent durability. On the other hand, polypropylene fibers having a fineness of 3000 dtex or less are preferred because they do not impair the flexibility of the fiber and fiber structure.

[0039] The elongation of the polypropylene fiber of the present invention is preferably adjusted by the production method described below depending on the application and required properties. Here, the elongation of the present invention refers to a value measured by the method described in the Examples. The higher the elongation, the more likely the fiber is to be elongated and not break even when subjected to sudden deformation. However, elongation during molding processing may cause the properties of the fiber product to become unstable. Therefore, in consideration of the handleability of the fiber, the elongation of the fiber of the present invention is more preferably 30 to 60%. In particular, an elongation of 60% or less is preferable because it improves the dimensional stability of the fiber and fiber structure.

[0040] The elongation of the polypropylene fiber of the present invention may be adjusted according to the required elongation for its intended use, and it is particularly preferred to adjust it to 30 to 50% for use in clothing applications, and 20 to 40% for use in non-clothing applications.

[0041] When at least a portion of the polypropylene fiber of the present invention is used to form a fiber structure, the fiber structure preferably has an apparent specific gravity of 1.0 or less. If the fiber structure has an apparent specific gravity of 1.0 or less, the bulkiness and light weight of the polypropylene fiber of the present invention are fully exhibited, and the fiber structure can be used as a lightweight fiber structure, which is preferable. The form of the fiber structure is not particularly limited, and it may be a knitted fabric, a woven fabric, a nonwoven fabric, or a structure incorporating binder fibers.

[0042] Next, the method for producing the polypropylene fiber of the present invention will be described below.

[0043] The polypropylene fiber of the present invention can be produced by a known melt spinning method or drawing method.

[0044] In the present invention, it is preferable to adjust the moisture content of the raw material to 0.3% by weight or less before melt spinning, and it is also preferable to dry the raw material as needed. A moisture content of 0.3% by weight or less is preferable because foaming due to moisture does not occur during melt spinning, allowing for stable spinning. Furthermore, if a thermoplastic resin is contained, this is preferable because, depending on the type, deterioration in mechanical properties and color tone due to hydrolysis is suppressed. A moisture content of 0.2% by weight or less is more preferable, and a moisture content of 0.1% by weight or less is even more preferable.

[0045] When polymer alloy spinning is performed, examples of a method for discharging from a spinneret to form a fiber yarn include, but are not limited to, the following. In a first example, composite chips are prepared by melt-kneading the sea component and island component components in advance using an extruder or the like to homogenize the sea-island structure, and the resulting chips are optionally dried. The chips are then supplied to a melt spinning machine to be melted and metered with a metering pump. The chips are then introduced into a heated spinning pack in a spinning block, the molten polymer is filtered in the spinning pack, and the resulting chips are discharged from the spinneret to form a fiber yarn. In a second example, the chips are optionally dried, the sea component and island component components are mixed in the chip state, the mixed chips are supplied to a melt spinning machine to be melted and metered with a metering pump. The chips are then introduced into a heated spinning pack in a spinning block, the sea component and island component polymers are kneaded and filtered in the spinning pack, and the resulting chips are discharged from the spinneret to form a fiber yarn. In a third example, composite chips having a higher weight percentage of island components than the final fiber composition are dried as needed, and then the composite chips and sea component chips are separately supplied and melted, and metered with a metering pump. The resulting mixture is then introduced into a heated spinning pack in a spinning block, where the sea-island component polymers are kneaded and filtered, and then discharged from a spinneret to form a fiber yarn. In a fourth example, composite chips having a higher weight percentage of island components than the final fiber composition are dried as needed, and then the composite chips and sea component chips are mixed in the chip state, where the mixed chips are supplied to a melt spinning machine, where they are melted, and then metered with a metering pump. The resulting mixture is then introduced into a heated spinning pack in a spinning block, where the sea-island component polymers are kneaded and filtered, and then discharged from a spinneret to form a fiber yarn.

[0046] The spinneret is preferably slit-shaped, and in order to increase the non-circularity M value, it is preferable that the slit width widens toward the outer periphery of the nozzle. It is preferable that the slit width at the outermost part is 1.2 to 2.0 times wider than the slit width closest to the center of the nozzle. A slit width of 1.2 times or more at the outermost part is preferable because the non-circularity M value is sufficient even when polypropylene, which has a high specific heat, has a high fiber temperature and continues to deform after being discharged from the spinneret. On the other hand, a slit width of 2.0 times or less at the outermost part is preferable because the non-circularity M value is sufficient and the protrusions on the fiber center side are prevented from becoming thinner, thereby preventing a decrease in abrasion resistance.

[0047] The fiber yarn discharged from the spinneret is cooled and solidified by a cooling device, taken up by a first godet roller, and wound by a winder via a second godet roller to produce a wound yarn. The tension during winding is preferably 0.05 to 0.10 cN / dtex. A winding tension of 0.05 cN / dtex or more is preferable because it ensures sufficient tension between the second godet roller and the winder, allowing for stable winding. On the other hand, a winding tension of 0.10 cN / dtex or less is preferable because it prevents deterioration of operability due to excessive yarn abrasion caused by high tension between the second godet roller and the winder, and it also prevents changes in the physical properties of the inner and outer layers of the wound yarn due to shrinkage over time. The fiber yarn may be oiled using an oiling device, or entangled using an entanglement device.

[0048] The spinning temperature in melt spinning can be appropriately selected depending on the melting point and heat resistance of each component in the fiber, but is preferably 220 to 300°C. A spinning temperature of 220°C or higher is preferable because the elongational viscosity of the fiber thread discharged from the spinneret is sufficiently reduced, resulting in stable discharge, and furthermore, the spinning tension does not become excessively high, thereby preventing thread breakage. A spinning temperature of 240°C or higher is more preferable. On the other hand, a spinning temperature of 300°C or lower is preferable because thermal decomposition during spinning can be suppressed, and the resulting polypropylene fiber can be prevented from decreasing in mechanical properties and coloring. A spinning temperature of 260°C or lower is more preferable.

[0049] The spinning speed in melt spinning can be selected appropriately depending on the composite ratio of each component in the fiber, the spinning temperature, etc., but is preferably 1000 to 3000 m / min in the case of a two-step method. A spinning speed of 1000 m / min or higher in the case of a two-step method is preferred because it stabilizes the running yarn and prevents yarn breakage. On the other hand, a spinning speed of 3000 m / min or lower in the case of a two-step method is preferred because it allows stable spinning without yarn breakage due to the suppression of spinning tension and also prevents changes in the physical properties of the inner and outer layers of the wound yarn due to shrinkage of the wound yarn after spinning. In the case of a one-step method in which spinning and drawing are performed simultaneously without winding, the spinning speed is preferably 1000 to 3000 m / min for the low-speed roller and 2500 to 6000 m / min for the high-speed roller. The low-speed roller and high-speed roller speeds within the above ranges are preferred because they stabilize the running yarn, prevent yarn breakage, and allow stable spinning.

[0050] When drawing is performed by a one-step method or a two-step method, either a one-stage drawing method or a multi-stage drawing method having two or more stages may be used. The heating method during drawing is not particularly limited as long as it is an apparatus that can directly or indirectly heat the running yarn.

[0051] The drawing temperature during drawing can be appropriately selected depending on the glass transition temperature and melting point of each component in the fiber, the strength and elongation of the fiber after drawing, etc., but is preferably 30 to 120°C. A drawing temperature of 30°C or higher is preferable because it ensures sufficient preheating of the yarn to be drawn, uniform thermal deformation during drawing, suppresses uneven fineness, and produces high-quality fibers with excellent uniformity in the longitudinal direction of the fiber. On the other hand, a drawing temperature of 120°C or lower is preferable because it suppresses fusion and thermal decomposition of the fibers due to contact with the heating roller, resulting in good processability and quality. It is also preferable because it improves the sliding properties of the fiber against the drawing roller, suppressing yarn breakage and enabling stable drawing. The drawing temperature is more preferably 90°C or lower. Furthermore, it is preferable to perform heat setting at 120 to 150°C. Heat setting at 120°C or higher is preferred because it allows the fibers to be sufficiently crystallized and prevents changes in the physical properties of the inner and outer layers of the drawn fiber due to shrinkage over time. On the other hand, a heat setting temperature of 150°C or lower is preferred because it prevents fusion between fibers and thermal decomposition, resulting in good processability and quality.

[0052] The draw ratio when drawing can be selected appropriately depending on the elongation of the fiber before drawing and the strength and elongation of the fiber after drawing, but is preferably 1.02 to 5.0 times. A draw ratio of 1.02 times or more is preferable because mechanical properties such as fiber strength and elongation can be improved by drawing. A draw ratio of 1.2 times or more is more preferable. On the other hand, a draw ratio of 5.0 times or less is preferable because yarn breakage during drawing is suppressed and stable drawing can be performed. A draw ratio of 3.5 times or less is more preferable.

[0053] The drawing speed when drawing can be selected appropriately depending on whether the drawing method is a one-step method or a two-step method. In the case of a one-step method, the speed of the high-speed roller at the above-mentioned spinning speed corresponds to the drawing speed. When drawing by a two-step method, the drawing speed is preferably 100 to 1000 m / min. A drawing speed of 100 m / min or more is preferred because it stabilizes the running yarn and prevents yarn breakage. On the other hand, a drawing speed of 1000 m / min or less is preferred because it prevents yarn breakage during drawing and allows stable drawing.

[0054] The method for producing the fiber structure of the present invention is not particularly limited, and any known method can be appropriately selected depending on the application and required properties. [Example]

[0055] The present invention will be described in more detail below with reference to examples. The characteristic values ​​in the examples were determined by the following methods.

[0056] A. Degree of irregularity M value The resulting fibers were embedded in epoxy resin and then cut perpendicular to the fiber axis using an LKB-2088 ultramicrotome. The embedded blocks were then coated with platinum-palladium alloy and micrographs were taken of the cross sections at magnifications ranging from 1,000 to 10,000x using a Hitachi S-4000 scanning electron microscope (SEM). Ten fibers were randomly selected from the resulting photographs, and the diameters of the circumscribed and inscribed circles of all fiber cross sections were measured using image processing software (WINROOF, manufactured by Mitani Corporation). The average values ​​of the 10 fibers were calculated and used to determine the diameter r1 (μm) of the circumscribed circle R1 and the diameter r2 (μm) of the inscribed circle R2 of the fiber cross section.

[0057] The irregularity M value is calculated using the diameter r1 of the circumscribed circle R1 and the diameter r2 of the inscribed circle R2 calculated above, using the following formula: Degree of irregularity M value = r1 / r2 It was calculated by:

[0058] B. Projection shape a / b, a / c In the fiber cross sections of the 10 fibers extracted from the photograph in A above, the maximum length a (μm) of the base where the protrusion is in contact with the inscribed circle R2, the width b (μm) of the protrusion when a straight line parallel to the base is drawn to the center of a perpendicular line drawn from the vertex where the protrusion is in contact with the circumscribed circle R1 to the base with the maximum length where the protrusion is in contact with the inscribed circle R2, and the length c (μm) of the perpendicular line drawn from the vertex where the protrusion is in contact with the circumscribed circle R1 to the base with the maximum length where the protrusion is in contact with the inscribed circle R2 were measured, and a / b and a / c were calculated, and their average values ​​were calculated.

[0059] C. Hollowness ratio The total cross-sectional area (S1) and the area of ​​the hollow portion (S2) in the fiber cross section of 10 fibers extracted from the photograph in A above were measured, and the hollow ratio (%) was calculated using the following formula.

[0060] Hollow rate (%)=(S2 / S1)×100 However, when multiple hollow portions exist in the cross section of the fiber, the sum of the areas of all the hollow portions was taken as the hollow portion area (S2), and the average value was taken as the hollow ratio (%).

[0061] D. Fineness 100 m of the resulting fiber was reeled out using an INTEC electric measuring machine under an environment of 20° C. and 65% RH. The weight of the resulting reel was measured, and the fineness (dtex) was calculated using the following formula. Fineness (dtex) = Weight of 100m of fiber (g) x 100 The measurement was carried out five times for each sample, and the average value was taken as the fineness.

[0062] E. Strength and elongation The strength and elongation were calculated using the resulting fibers as samples in accordance with JIS L1013:2010 (Testing Methods for Chemical Fiber Filament Yarns) 8.5.1. Tensile tests were conducted using an Orientec Tensilon UTM-III-100 under conditions of 20°C temperature and 65% RH, with an initial sample length of 20 cm and a tensile speed of 20 cm / min. The stress (cN) at the point showing the maximum load was divided by the fineness (dtex) to calculate the strength (cN / dtex), and the elongation (L1) at the point showing the maximum load and the initial sample length (L0) were used to calculate the elongation (%) according to the following formula: Elongation (%)={(L1-L0) / L0}×100 The measurement was carried out 10 times for each sample, and the average values ​​were used as the strength and elongation.

[0063] F. Apparent specific gravity For fibers without hollow cores, the apparent specific gravity was calculated in accordance with JIS L1013:2010 (Testing Methods for Chemical Fiber Filament Yarns) 8.17.1 (Specific Gravity (Floating-Sinking Method)). A specific gravity measurement solution was prepared using water as the heavy liquid and ethyl alcohol as the light liquid. Approximately 0.1 g of sample was left in the specific gravity measurement solution for 30 minutes in a thermostatic bath at 20±0.1°C, and the floating-sinking state of the sample was then observed. Depending on the floating-sinking state, heavy or light liquid was added, and the sample was left for another 30 minutes. Once the sample had reached a floating-sinking equilibrium state, the specific gravity of the specific gravity measurement solution was measured, and the specific gravity of the sample was calculated.

[0064] For fibers with hollow portions, the apparent specific gravity (d1) of a fiber of the same composition but without hollow portions was calculated by the sink-float method described above, and the hollowness (h (%)) calculated from D described above was used to calculate the apparent specific gravity (d2) of the fiber with hollow portions using the following formula. d2=d1×(100-h)÷100 The apparent specific gravities of the knitted fabrics of Examples 25 to 30 and Comparative Example 3 were calculated based on the blend ratios of the water-repellent fibers and hydrophilic fibers constituting the knitted fabrics calculated under the above conditions.

[0065] G. Abrasion resistance The resulting fibers were used as samples to knit approximately 2 g of tubular fabric using an Eiko Sangyo NCR-BL circular knitting machine (3.5 inch (8.9 cm) diameter, 27 gauge). The fabric was then scoured for 20 minutes at 80°C in an aqueous solution containing 1.5 g / L sodium carbonate and 0.5 g / L Meisei Chemical Co., Ltd. surfactant "Grand Up" US-20. The scoured tubular fabric was then dry-heat set at 135°C for 1 minute. The dry-heat set tubular fabric was used as a sample. It was rubbed 100 times with a 2 N load using the friction tester type II (Gakushin type) method described in JIS 0849 (2013). The change in cross-sectional shape was confirmed according to the above-mentioned "A. Observation of fiber cross-sectional shape." The results were rated on a four-point scale: S, A, B, and C. S was the best, A was next, B was next, and C was the worst. "No change in cross-sectional shape" was rated as S, "some change in cross-sectional shape" was rated as A, "clear change in cross-sectional shape" was rated as B, and "significant change in cross-sectional shape" was rated as C.

[0066] H. Water repellency The obtained fiber was wound around a plate using an Eiko Sangyo aligned winding evaluation device (model SAW-S05-60) with a winding pitch of 0.3 mm and 8 traverses. The plate was then immersed in ethanol for 24 hours to remove the oil. The resulting plate was used as a sample, and its water repellency was evaluated using a Kyowa Interface Science contact angle meter, DropMaster (DMo-501SA).

[0067] The contact angle was measured by fixing the plate so that the fiber was wound horizontally relative to the camera's line of sight, dropping a 2 μL droplet of water on the plate, and measuring the contact angle. Measurements were performed five times for each sample, and the average value was taken as the contact angle.

[0068] The sliding angle was measured by fixing the plate winding so that the fiber was wound perpendicular to the camera's line of sight, dropping a 7 μL droplet of water onto the plate, and rotating the tilt angle from 0 to 90 degrees at a rate of 1° / second. The angle at which the droplet slid down and disappeared from the camera image was measured. Measurements were made five times for each sample, and the average value was taken as the sliding angle.

[0069] I. Island discontinuity The resulting fibers were embedded in epoxy resin and then cut perpendicular to the fiber axis using an LKB-2088 ultramicrotome (LKB). Ultrathin sections approximately 100 nm thick were obtained. The resulting ultrathin sections were stained by exposing them to ruthenium tetroxide vapor at room temperature for approximately 4 hours. The stained surfaces were then cut with an ultramicrotome to produce ruthenium tetroxide-stained ultrathin sections. The stained ultrathin sections were then observed at intervals of at least 10,000 times the fiber diameter within each single fiber using a Hitachi H-7100FA transmission electron microscope (TEM) at an accelerating voltage of 100 kV. Five micrographs of the fiber cross sections were taken. When the number of island components and the shape of the sea-island structure in each fiber cross section were different in the photographs, the island components were judged to be discontinuous, and the case where the island components were discontinuous was rated "Y", and the case where the island components were not discontinuous was rated "N".

[0070] JL * value The dry-heat-set cylindrical knit fabric obtained in G above was dyed for 45 minutes at 130°C in a dyeing solution containing 3.0% by weight of Huntsman TERATOP Blue NFB as a disperse dye and adjusted to a pH of 5.0, at a bath ratio of 1:30. The dyed cylindrical knit fabric was then reduced-washed for 20 minutes at 80°C in an aqueous solution containing 2 g / L of sodium hydroxide, 2 g / L of sodium dithionite, and 0.5 g / L of Meisei Chemical Industry's surfactant "Grand Up" US-20 at a bath ratio of 1:30. It was then rinsed for 30 minutes in running water and dried for 60 minutes in a hot-air dryer at 60°C. The reduced-washed cylindrical knit fabric was dry-heat-set for 1 minute at 135°C for a finishing set. The cylindrical knitted fabric after finishing and setting was used as a sample, and the L * The measurement was carried out three times for each sample, and the average value was calculated as L * The value was set as

[0071] K. Water absorption The surface of the obtained knitted fabric with a higher area occupancy rate of the water-repellent fibers was designated as the surface, and the water absorbency of the surface was evaluated in accordance with JIS L1907:2010 (Water absorption test method for textile products) 7.1.1 (Drop method).

[0072] Furthermore, the water absorbency was evaluated in the same manner after 100 washes. The washing method was in accordance with JIS L0217:1995 (labeling symbols and labeling methods for handling textile products) 103 method.

[0073] Example 1 Polypropylene (PP) (ExxonMobil PP3155E5, melting peak temperature 163°C, MFR 36 g / 10 min) was fed into an extruder-type melt spinning machine and melted. The melt was then extruded at a spinning temperature of 240°C and a throughput of 28.0 g / min through a spinneret (discharge slit width (center) 0.07 mm, discharge slit width (periphery) 0.10 mm, discharge hole length 0.35 mm, number of holes 48, six-lobe hole) to obtain a spun yarn. The spun yarn was cooled with cooling air at a temperature of 20°C and a speed of 25 m / min, oiled with an oiling device, and converged. The yarn was taken up by a first godet roller rotating at 2000 m / min, passed through a second godet roller rotating at the same speed as the first godet roller, and wound by a winder to obtain a 140 dtex-48 f undrawn yarn. The obtained undrawn yarn was drawn under the conditions of a first hot roller temperature of 30°C, a second hot roller temperature of 140°C, and a draw ratio of 2.5 times to obtain a drawn yarn of 56 dtex-48f.

[0074] The evaluation results of the fiber properties and fabric properties of the obtained fiber are shown in Table 1. The obtained polypropylene fiber was excellent in both abrasion resistance and water repellency.

[0075] (Examples 2 to 4, Comparative Examples 1 and 2) A drawn yarn was produced in the same manner as in Example 1, except that the M value was changed to a spinneret that gave a cross-sectional shape as shown in Table 1.

[0076] The evaluation results of the fiber properties and fabric properties of the obtained fibers are shown in Table 1. Comparative Example 1 had poor water repellency due to the round cross section, and Comparative Example 2 had poor abrasion resistance.

[0077] ( Reference examples 5, 8, Example 6、7、9 ~12) A drawn yarn was produced in the same manner as in Example 1, except that the values ​​of the projection shapes a / b and a / c were changed to a spinneret that would give a cross-sectional shape as shown in Table 2.

[0078] The evaluation results of the fiber properties and fabric properties of the obtained fiber are shown in Table 2. reference In Example 8, the a / b value of the projection shape is large, meaning that the projection shape is tapered, which reduces wear resistance. Ta.

[0079] ( Reference examples 13, 14, Example 15、 16) A drawn yarn was produced in the same manner as in Example 1, except that the number of protrusions was changed to a die having a cross-sectional shape as shown in Table 3.

[0080] The evaluation results of the fiber properties and fabric properties of the obtained fiber are shown in Table 3. As the number of protrusions increased, the water repellency improved.

[0081] (Examples 17 to 21) A drawn yarn was produced in the same manner as in Example 1, except that the spinneret was changed to one that would give a cross-sectional shape with a hollow ratio as shown in Table 3.

[0082] The evaluation results of the fiber properties and fabric properties of the obtained fibers are shown in Table 3. As the hollow ratio increased, the fiber became lighter, but the strength and abrasion resistance decreased.

[0083] Examples 22 to 24 Drawn yarns were prepared in the same manner as in Example 1 for Example 22, Example 18 for Example 23, and Example 19 for Example 24, except that the polymer types were changed to 89.0 wt% of PP (PP3155E5 manufactured by ExxonMobil) as the sea component, 10.0 wt% of polyethylene terephthalate copolymerized with 35 mol% of 1,4-cyclohexanedicarboxylic acid as the island component, and 1.0 wt% of a styrene-butadiene-butylene-styrene copolymer having an amino group as a functional group as a compatibilizer (TUFTECH MP10 manufactured by Asahi Kasei).

[0084] The evaluation results of the fiber properties and fabric properties of the obtained fiber are shown in Table 4. These results confirmed that dyeable highly modified cross-section polypropylene fiber was successfully produced.

[0085] Example 25 A reversible jersey knit fabric was knitted using the polypropylene fiber obtained in Example 1 as the water-repellent fiber, with the weight ratio of the water-repellent fiber expressed as a percentage of the knit fabric weight, with the water-repellent fiber on the needle surface and an 84 dtex-48f polyethylene terephthalate yarn as the hydrophilic fiber on the sinker surface. The knit fabric was scoured at 80°C for 20 minutes in an aqueous solution containing 1.5 g / L of sodium carbonate and 0.5 g / L of Meisei Chemical Industry's surfactant "Grand Up" US-20, then rinsed with running water for 30 minutes and dried in a hot air dryer at 60°C for 60 minutes. The scoured knit fabric was then dry-heat set at 135°C for 1 minute.

[0086] The properties of the obtained knitted fabric are shown in Table 5. The water absorbency was 60 seconds or more both initially and after 100 washes, demonstrating excellent water repellency and washing durability.

[0087] (Examples 26 to 30) A knitted fabric was prepared in the same manner as in Example 25, except that the water-repellent fibers used and their blending ratios were changed as shown in Table 5.

[0088] The properties of the obtained knitted fabric are shown in Table 5. It can be seen that by using hollow fibers, it was possible to knit a lightweight knitted fabric with an apparent specific gravity of 1.0 or less and excellent water repellency.

[0089] (Comparative Example 3) A knitted fabric was prepared in the same manner as in Example 25, except that the water-repellent fiber used was changed to a water-repellent polyethylene terephthalate yarn of 84 dtex-48 f. Here, the water-repellent polyethylene terephthalate yarn is a polyethylene terephthalate fiber that has been treated to be water-repellent by absorbing the water-repellent agent in a dyeing bath in a cheese dyeing machine, and the water-repellent agent used was an environmentally friendly fluorine-based water-repellent agent containing 2.0 wt% of perfluorooctanoic acid and perfluorooctanesulfonic acid at a concentration of 0 to 5 ng / g or less.

[0090] The properties of the obtained knitted fabric are shown in Table 5. The apparent specific gravity was 1.4, which was heavy, and the initial water absorbency was 60 seconds or more, showing excellent water repellency. However, after 100 washes, the water absorbency was only 1 second, indicating that the water repellency decreased with washing.

[0091] [Table 1]

[0092] [Table 2]

[0093] [Table 3]

[0094] [Table 4]

[0095] [Table 5] [Industrial Applicability]

[0096] The polypropylene fiber of the present invention is bulky and has an excellent feel, and can be suitably used as a fiber structure.

Claims

1. A polypropylene fiber characterized in that the fiber cross section has an irregularity M value of 1.2 to 3.0, has five or more protrusions protruding radially from the center of the fiber cross section, and the protrusion shape a / b of the protrusions is 1.5 or more and 3.0 or less. * Irregularity M value = r1 / r2 where r1 is the diameter (μm) of the circumscribing circle R1 of the cross section of a single fiber, r2 is the diameter (μm) of the inscribing circle R2 of the cross section of a single fiber, a is the maximum length (μm) of the base where the protrusion is in contact with the inscribing circle R2 in the cross section of a single fiber, and b is the width (μm) of the protrusion when a straight line parallel to the base is drawn to the center of the perpendicular line from the vertex where the protrusion is in contact with the circumscribing circle R1 to the base having the maximum length where the protrusion is in contact with the inscribing circle R2.

2. 2. The polypropylene fiber according to claim 1, which has at least one hollow portion, and the hollow portion has a void ratio of 10% to 50%.

3. A fiber structure comprising at least a part of the polypropylene fiber according to claim 1 or 2.

4. The fiber structure according to claim 3 , having an apparent specific gravity of 1.0 or less.

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