Short polypropylene fiber

Abstract

This short polypropylene fiber is characterized by: being a short polymer alloy fiber having a sea-island structure in which a polypropylene (A) is a sea component and a thermoplastic resin (B) having a polar functional group is an island component; having, exposed on the surface thereof, the thermoplastic resin (B) that has a polar functional group; and having a fiber length of 20-100 mm and a single fiber fineness of 0.5-3.5 dtex.　Provided is a short polypropylene fiber that has improved abrasion resistance while having characteristics of polypropylene, that has excellent texture, and that can be suitably used for a spun yarn.

Description

Polypropylene short fiber

[0001] The present invention relates to polypropylene staple fibers.

[0002] Polypropylene fibers, a type of polyolefin fiber, are lightweight and chemically resistant, making them useful in a variety of fields, including interior applications such as tile carpets, household rugs, and car mats, as well as materials such as ropes, protective netting, narrow tape, braided cords, and upholstery. However, because polypropylene lacks polar functional groups, it does not form intermolecular hydrogen bonds between single fibers like natural fibers such as cotton and silk. Therefore, when used as short fibers, polypropylene is prone to pilling and exhibits poor abrasion resistance. To improve the abrasion resistance of fiber structures using short polypropylene fibers, physical methods such as increasing interfiber entanglement or thermal bonding have been proposed. However, increasing interfiber entanglement results in a thicker and larger fiber structure, while thermal bonding results in fusion and solidification, both of which result in poor texture. One possible method for improving abrasion resistance while avoiding such deterioration in texture is to introduce polar functional groups into polypropylene fibers to impart chemical interactions between the single fibers.

[0003] As methods for introducing polar functional groups into polypropylene fibers, Patent Documents 1 and 2 disclose a method using modified polypropylene in which polar functional groups have been introduced into the polymer chain of polypropylene, Patent Document 3 discloses a surface treatment method such as corona discharge treatment or low-temperature plasma treatment, and Patent Document 4 discloses a method of applying a fiber treatment agent.

[0004] JP 2009-108427 A JP 2016-65357 A JP 2000-80559 A JP 10-53955 A

[0005] In Patent Document 1, modified polypropylene is used to improve compatibility with different raw materials, and although the improvement in compatibility between the raw materials can be confirmed, there is no mention of chemical interactions between single fibers.

[0006] In Patent Document 2, modified polypropylene is used as a fiber reinforcing agent, and although it is possible to confirm an improvement in adhesion to different materials such as carbon fiber, it is ultimately melted and becomes resinous, so it is not possible to confirm an improvement in the physical properties of the fiber or chemical interactions between individual fibers.

[0007] In Patent Document 3, hydrophilicity is achieved by treating the surface of the fabric to introduce polar functional groups, but the fiber strength is deteriorated and the method is uneconomical.

[0008] In Patent Document 4, polar functional groups are introduced using a fiber treatment agent to achieve hydrophilicity of the fabric surface, but this study is aimed at nonwoven fabric applications that do not require washing, and the fiber treatment agent gradually detaches with repeated washing, making this method unsuitable for applications requiring washing durability, such as clothing applications. Furthermore, in Patent Documents 3 and 4, polar functional groups are introduced for the purpose of hydrophilization, so the water repellency that is a characteristic of polypropylene is lost, and this method is unsuitable for applications requiring water repellency.

[0009] As described above, polypropylene staple fibers are excellent in terms of light weight, chemical resistance, and water repellency, and therefore there is a demand for the development of polypropylene staple fibers that have improved abrasion resistance by introducing polar functional groups while maintaining these inherent properties of polypropylene. Therefore, an object of the present invention is to solve the technical problems related to polypropylene staple fibers described above and to provide polypropylene staple fibers that have improved abrasion resistance while retaining the properties of polypropylene, have excellent texture, and are particularly suitable for use as spun yarns.

[0010] The above problems can be solved by: (1) a polymer alloy staple fiber having an island-sea structure in which polypropylene (A) is a sea component and thermoplastic resin (B) having a polar functional group is an island component, wherein the thermoplastic resin (B) having a polar functional group is exposed on the surface, and the polypropylene staple fiber is characterized by having a fiber length of 20 to 100 mm and a single fiber fineness of 0.5 to 3.5 dtex; (2) a polypropylene staple fiber according to (1), characterized in that the thermoplastic resin (B) having a polar functional group is polyester; (3) a polypropylene staple fiber according to (1) or (2), characterized in that it contains a compatibilizer (C); and (4) a spun yarn characterized in that it contains 20 to 80% by weight of the polypropylene staple fiber according to any one of (1) to (3).

[0011] According to the present invention, it is possible to provide polypropylene staple fibers that have improved abrasion resistance and excellent texture while retaining the properties of polypropylene, and that can be suitably used as fiber structures. The polypropylene staple fibers obtained by the present invention can be spun into yarns, and can be suitably used in applications where excellent abrasion resistance and texture are particularly required, in addition to applications where conventional polypropylene staple fibers are used.

[0012] The polypropylene short fiber of the present invention is a polymer alloy short fiber having an island-sea structure in which polypropylene (A) is a sea component and thermoplastic resin (B) having a polar functional group is an island component, in which the thermoplastic resin (B) having a polar functional group is exposed on the surface, and the fiber length is 20 to 100 mm and the single fiber fineness is 0.5 to 3.5 dtex.

[0013] The polymer alloy short fiber in the present invention refers to a short fiber in which island components are discontinuously dispersed. Here, the discontinuous island components mean that the island components are present with an appropriate length in the longitudinal direction of the fiber, the length being 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., fiber cross sections, 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.

[0014] When island components are discontinuously dispersed, the specific interfacial area of ​​the sea-island interface can be sufficiently increased, thereby suppressing interfacial delamination and producing polymer alloy short fibers with excellent mechanical properties and abrasion resistance. Furthermore, part of the island components can be exposed on the fiber surface, and the fiber surface is not covered solely by the sea component, so that the properties of both the sea component and the island component are more significantly exhibited as fiber surface properties. As described above, the polymer alloy short fiber of the present invention is essentially different from a core-sheath composite fiber in which one island is formed continuously and uniformly in the fiber axis direction, or a sea-island composite fiber in which multiple islands are formed continuously and uniformly in the fiber axis direction. Such polymer alloy short fibers can be obtained, for example, by molding a polymer alloy composition formed by kneading polypropylene (A) and a thermoplastic resin (B) having a polar functional group at any stage before the completion of melt spinning.

[0015] In the polypropylene short fiber of the present invention, the thermoplastic resin (B) having a polar functional group is exposed on the surface. When the only component present on the surface is polypropylene (A), the polypropylene does not have a polar functional group, so there is no uneven distribution of electrons. When a fiber structure is formed, there is no chemical interaction between closely spaced single fibers, and therefore, when external stress such as friction is applied, fuzzing is likely to occur. Therefore, in order to prevent fuzzing, the only way to do this is to physically entangle the single fibers tightly, but this can only be achieved by increasing the fiber length to strengthen the twist or by thermally fusing the single fibers together. In addition, the texture is also limited, making it difficult to obtain a wide variety of textures when used alone or in combination with other materials. On the other hand, when the thermoplastic resin (B) having polar functional groups is exposed on the surface, a chemical interaction occurs between closely spaced single fibers when the fiber structure is made, due to the uneven distribution of electrons derived from the polar functional groups of the thermoplastic resin (B) having polar functional groups, and fuzzing due to external stress can be suppressed without strengthening the physical entanglement, making it possible to create a variety of textures when used alone or in combination with other materials. In addition, the chemical interaction between the single fibers increases the bundling ability, suppressing fuzzing and shedding of single yarns during processing, and improving processability.

[0016] The sea component constituting the sea-island structure of the polypropylene short fibers of the present invention is polypropylene (A).

[0017] The polypropylene (A) of the present invention may be a propylene homopolymer or a copolymer with other α-olefins. One or more of the other α-olefins may be copolymerized.

[0018] The island components constituting the sea-island structure of the polypropylene short fibers of the present invention are thermoplastic resin (B) having a polar functional group.

[0019] The polypropylene short fibers of the present invention preferably contain 5.0 to 20.0 parts by weight of a thermoplastic resin (B) having polar functional groups per 100 parts by weight of the total fiber composition. A content of 5.0 parts by weight or more of the thermoplastic resin (B) having polar functional groups is preferred because the introduction of polar functional groups sufficiently promotes chemical interaction between the individual fibers, improving abrasion resistance. On the other hand, a content of 20.0 parts by weight or less of the thermoplastic resin (B) having polar functional groups is preferred because the hydrophilicity caused by the introduction of a large amount of polar functional groups is not significant and the water repellency characteristic of polypropylene fibers is not impaired. The effect of introducing these thermoplastic resins (B) having polar functional groups can be easily confirmed by measuring the contact angle. The contact angle measurement method is as described in the Examples. By including the thermoplastic resin (B) having polar functional groups, the thermoplastic resin (B) having polar functional groups is exposed on the fiber surface, increasing hydrophilicity, resulting in a smaller contact angle. In order to fully develop chemical interactions between single fibers and improve abrasion resistance, the contact angle is preferably 146° or less, and more preferably 143° or less. On the other hand, in order not to impair the water repellency, which is a characteristic of polypropylene fibers, the contact angle is preferably 135° or more, and more preferably 138° or more.

[0020] Specific examples of the thermoplastic resin (B) having a polar functional group of the present invention include, but are not limited to, polyester, polyamide, acrylic, modified polypropylene, modified polyethylene, etc. Among these, polyester and polyamide are preferred because they stably have many polar functional groups, and polyester is more preferred because it has a shorter HSP distance with polypropylene calculated from the Hansen solubility parameter (HSP), which is an indicator of affinity, and has good dispersibility.

[0021] The polyester preferred in the present invention is mainly composed of terephthalic acid and ethylene glycol, and may have a polymer component. Examples of copolymerized dicarboxylic acid components include 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.

[0022] In the polymer alloy staple fiber of the present invention, a compatibilizer (C) may be added as needed to improve the dispersibility of the island components (thermoplastic resin (B)) in the polypropylene sea component (A), control the dispersion state, improve the interfacial adhesion between the polypropylene sea component (A) and the island components, and increase the surface area of ​​the island components on the surface of a single fiber. Furthermore, when forming an island-sea structure by melt spinning, a bulge called ballas tends to occur just below the spinneret, making the thinning deformation of the fiber unstable. Therefore, it is preferable to use a compatibilizer to improve spinning operability, such as by suppressing yarn breakage associated with this ballas, and to obtain high-quality fibers with small fineness unevenness and excellent uniformity in the fiber longitudinal direction.

[0023] The compatibilizer (C) in the present invention can be appropriately selected depending on the composition of the polypropylene (A) of the sea component and the island component, the conjugation ratio of the polypropylene (A) of the sea component and the island component, etc. Only one type of compatibilizer may be used, or two or more types may be used in combination.

[0024] When a compatibilizer is added, the polypropylene staple fiber of the present invention preferably contains 0.1 to 10.0 parts by weight of the compatibilizer (C) 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 sea component polypropylene (A) 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. Furthermore, a smaller dispersion diameter of the island component fibers increases the surface area of ​​the island component fibers and the proportion of the island component fibers on the fiber surface, which is also preferred because it strengthens the chemical interaction between the individual fibers. Furthermore, this is preferred because it improves spinning operability, such as suppressing yarn breakage, and also enables the production of high-quality fibers with small fineness unevenness and excellent uniformity in the fiber longitudinal direction. On the other hand, if the content of the compatibilizer (C) is 10.0 parts by weight or less, the fiber properties, appearance, and texture derived from the polypropylene (A) of the sea component and the island component constituting the polypropylene short fibers can be maintained, which is preferable, and the instability of spinning operability due to an excessive amount of the compatibilizer can be suppressed.

[0025] The polypropylene short fibers of the present invention preferably contain 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.

[0026] 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.

[0027] Next, the form of the polypropylene short fibers of the present invention will be described.

[0028] The polypropylene short fibers of the present invention have a fiber length of 20 to 100 mm. If the polypropylene short fibers have a fiber length of 20 mm or more, the entanglement and chemical interaction between the single fibers are sufficient, the processability after cutting into short fibers is excellent, and fluffing is suppressed during the formation of a fiber structure. The polypropylene short fibers preferably have a fiber length of 35 mm or more. On the other hand, if the polypropylene short fibers have a fiber length of 100 mm or less, the entanglement between the single fibers is sufficient, and a texture unique to short fibers is produced. In addition, problems with processability are unlikely to occur. The polypropylene short fibers preferably have a fiber length of 80 mm or less.

[0029] The single fiber fineness of the polypropylene staple fiber of the present invention can be appropriately selected depending on the application and required properties, but is in the range of 0.5 to 3.5 dtex. The single fiber fineness in the present invention is measured by the method described in the Examples section. If the single fiber fineness of the polypropylene staple fiber is 0.5 dtex or more, there is little thread breakage, and the surface area of ​​the single fiber is sufficiently large to exhibit chemical interactions and improve processability. In addition, there is little generation of fluff during use, and durability is excellent. On the other hand, if the single fiber fineness of the polypropylene staple fiber is 3.5 dtex or less, the flexibility of the fiber and fiber structure is not impaired. The single fiber fineness of the polypropylene staple fiber is preferably 3.0 dtex or less.

[0030] The cross-sectional shape of the polypropylene staple fiber of the present invention is not particularly limited, and can be appropriately selected depending on the application and required properties. It may have a circular cross section or a noncircular cross section. Specific examples of noncircular cross sections include, but are not limited to, multilobal, polygonal, flat, elliptical, C-shaped, H-shaped, S-shaped, T-shaped, W-shaped, X-shaped, Y-shaped, square-shaped, and hollow. Among these, multilobal shapes are preferred because they increase the intermolecular forces between single fibers, thereby increasing the surface area and the adhesive area between closely spaced single fibers. Hollow shapes are also preferred because they increase the surface area of ​​single fibers and also improve the lightweight property, which is a characteristic of polypropylene.

[0031] Next, the method for producing the polypropylene short fibers of the present invention will be described below.

[0032] The polypropylene short fibers of the present invention can be produced by a known melt spinning method or crimping method.

[0033] In the present invention, it is preferable to set the moisture content of the raw material to 0.3% by weight or less before melt spinning, and it is therefore 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. This is also preferable because, depending on the type of thermoplastic resin, 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.

[0034] When melt spinning a polymer alloy fiber, examples of a method for discharging the chips from a spinneret to form a fiber thread include, but are not limited to, the following. In a first example, composite chips are prepared by melt-mixing 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 thread. 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 components are mixed in the spinning pack, and the resulting mixture is 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 mixed and filtered in the spinning pack, and the resulting mixture is then discharged from the spinneret to form a fiber thread. In a third example, composite chips having a higher weight percentage of island components than that of 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 that of the final fiber composition are dried as needed, and then the composite chips and sea component chips are mixed in the chip state, and then the mixed chips are supplied to a melt spinning machine, where they are 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.

[0035] The yarn spun in the melt spinning can be once wound up and then supplied to the crimping step, once gathered into a tow without being wound up and collected, and then supplied to the crimping step, or continuously supplied to the crimping step without being wound up or collected.

[0036] When the spun yarn in melt spinning is temporarily wound up, 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 form a wound yarn, or the fiber yarn is taken up by a heated first roller, stretched between a heated second roller, and then wound by a winder via a third godet roller and a fourth godet roller to form a wound yarn, but this is not limited to these methods. In addition, the fiber yarn may be oiled using an oiling device, or entangled using an entanglement device.

[0037] Crimping can be performed in the crimping step. Methods for crimping include, but are not limited to, the stuffer box method, the indentation heating gear method, and the high-speed air injection indentation method. Furthermore, if necessary, an oil agent can be suitably applied as a finishing agent before or after crimping. The crimped or uncrimped fiber bundles are cut to fiber lengths of 20 to 100 mm using a known cutter. The polypropylene staple fibers of the present invention cut to fiber lengths of 20 to 100 mm have polar functional groups exposed on the surface, which allows for chemical interactions between the individual fibers, resulting in excellent processability and reduced fuzzing during the formation of a fiber structure.

[0038] The polypropylene short fibers of the present invention can be used as fiber structures such as spun yarns and nonwoven fabrics, and are particularly preferably used as spun yarns.

[0039] There are no particular limitations on the method for producing a spun yarn containing at least a portion of the polypropylene staple fiber of the present invention. Blending with other fibers can be performed using known methods, such as raw cotton blending, lap blending, and sliver blending, depending on the intended application and required properties. For spun yarns containing at least a portion of polypropylene staple fibers, it is preferable that the fibers other than the polypropylene staple fibers also have polar functional groups. When the fibers other than the polypropylene staple fibers also have polar functional groups, chemical interactions occur between the polar functional groups exposed on the surface of the polypropylene staple fibers of the present invention and the fibers, resulting in good processability, less fuzz generation during use, and excellent durability. Examples of such fibers include, but are not limited to, animal hair such as wool, natural fibers such as cotton, hemp, and silk, synthetic fibers such as polyester, nylon, and acrylic fibers, and semi-synthetic and regenerated fibers. When blending the polypropylene staple fibers of the present invention with the aforementioned fibers having polar functional groups, blending is preferably performed early in the production process to enhance the chemical interactions between the polypropylene staple fibers and the other fibers. The proportion of polypropylene staple fibers in the spun yarn is preferably 20 to 80% by weight. It is preferable that the polypropylene staple fiber content is 20% by weight or more, since the water repellency and light weight properties of polypropylene can be imparted to the spun yarn.Also, it is preferable that the proportion of polypropylene staple fiber is 80% by weight or less, since the water repellency and light weight properties of polypropylene are prominent and the properties of the other blended materials are imparted to the spun yarn.

[0040] 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.

[0041] A. Conjugation ratio The total of the sea component (A), island component (B) and compatibilizer (C) used as raw materials for the polypropylene short fiber was taken as 100 parts by weight, and the conjugation ratio was calculated as sea component (A) / island component (B) / compatibilizer (C) [parts by weight].

[0042] B. Fiber length and single fiber fineness Measured in accordance with JIS L1015:2010 (chemical fiber staple test method).

[0043] C. Contact Angle The obtained fiber was wound onto a plate using an aligned winding evaluation device (model SAW-S05-60) manufactured by Eiko Sangyo Co., Ltd. at a winding pitch of 0.3 mm with 8 traverses, and then the plate was immersed in ethanol for 24 hours to remove the oil. This plate was used as a sample and evaluated using a contact angle meter DropMaster (DMo-501SA) manufactured by Kyowa Interface Science Co., Ltd.

[0044] The contact angle was measured by fixing the plate winding so that the fiber was wound horizontally relative to the camera's line of sight, dropping a 2 μL droplet of water on the fiber, and measuring the contact angle. Measurements were performed five times for each sample, and the average value was taken as the contact angle.

[0045] D. Island Component Discontinuity The fibers obtained in the examples were embedded in epoxy resin, and then cut together with the epoxy resin in a direction perpendicular to the fiber axis using an LKB-2088 ultramicrotome manufactured by LKB to obtain ultrathin sections with a thickness of approximately 100 nm. The obtained ultrathin sections were stained by holding them in a vapor phase of ruthenium tetroxide at room temperature for approximately 4 hours, and then the stained surfaces were cut with an ultramicrotome to prepare ultrathin sections stained with ruthenium tetroxide. The stained ultrathin sections were observed at cross sections perpendicular to the fiber axis, i.e., fiber cross sections, within the same single fiber at arbitrary intervals of at least 10,000 times the single fiber diameter using a Hitachi H-7100FA transmission electron microscope (TEM) at an accelerating voltage of 100 kV, and 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 as "Y", and the case where the island components were not discontinuous was rated as "N".

[0046] E. Abrasion Resistance Approximately 2 g of cylindrical knitted fabric was prepared using the fibers obtained in the examples as raw materials, and then the fabric was scoured for 20 minutes at 80°C in an aqueous solution containing 1.5 g / L of sodium carbonate and 0.5 g / L of Meisei Chemical Industry's surfactant Gran Up US-20. The fabric was then rinsed with running water for 30 minutes and dried for 60 minutes in a hot air dryer at 60°C. The dried cylindrical knitted fabric was dry-heat set at 135°C for 1 minute, placed on the top and bottom of an appearance retention tester described in JIS L1076:2012, and abraded for 10 minutes at a pressure of 7.4 N. The change in fuzz (fibrillation) before and after abrasion was observed at 50x magnification using a Keyence Corporation VHX-2000 microscope, and evaluated on a three-level scale of S, A, and B. S indicates the best, A indicates the next best, and B indicates the worst. "No change (no fibrillation)" was rated as S, "some fibrillation" as A, and "clear fibrillation" as B.

[0047] F. Quality The cylindrical knitted fabrics produced in E above after dry heat setting were evaluated on a four-point scale of S, A, B, and C by a consensus of five inspectors with at least five years of experience in evaluating quality. S indicates the best quality, followed by A and B, and C indicates the worst quality. S indicates "extremely excellent quality," A indicates "excellent quality," B indicates "poor quality," and C indicates "extremely poor quality."

[0048] Example 1 A blending ratio of 90.0 wt % of polypropylene (PP) (PP3155E5 manufactured by ExxonMobil, melting peak temperature 163°C, MFR 36 g / 10 min) as the sea component and 10.0 wt % of polyethylene terephthalate copolymerized with 35 mol % of 1,4-cyclohexanedicarboxylic acid as the island component was performed using a twin-screw extruder at a blending temperature of 230°C. The strands extruded from the twin-screw extruder were water-cooled and then cut into approximately 5 mm lengths using a pelletizer to obtain composite chips. The obtained composite chips were vacuum-dried at 90°C for 12 hours, fed to an extruder-type melt spinning machine to melt, and extruded from a spinneret (nozzle diameter 0.20 mm, nozzle length 0.50 mm, number of holes 96, round holes) at a spinning temperature of 240°C at a throughput rate of 33.0 g / min to obtain spun yarns. The spun yarn was cooled with cooling air at a temperature of 20°C and a speed of 25 m / min, and then oiled and converged using an oiling device. The yarn was then taken up by a first godet roller rotating at 1000 m / min, passed through a second roller rotating at 3000 m / min and heated to 140°C, a third godet roller rotating at 2950 m / min, and a fourth godet roller, and wound on a winder at a winding tension of 0.08 cN / dtex to obtain a polymer alloy long fiber. This long fiber was mechanically crimped by a push-in method, then subjected to a relaxation heat treatment at 150°C, and then cut to obtain a polymer alloy staple fiber having a single fiber fineness of 1.2 dtex and a fiber length of 51 mm. This staple fiber was then used as a spun yarn.

[0049] The evaluation results of the fiber properties and fabric properties of the obtained spun yarn are shown in Table 1.

[0050] Examples 2 to 4, Comparative Example 1 Spun yarns were prepared in the same manner as in Example 1, except that 1.0 wt % of a styrene-butadiene-butylene-styrene copolymer (Tuftec MP10 manufactured by Asahi Kasei Co., Ltd.) having an amino group as a functional group was added as a compatibilizer, and the conjugation ratios of the sea component and the island component were changed as shown in Table 1.

[0051] The evaluation results of the fiber properties and fabric properties of the obtained spun yarn are shown in Table 1. Comparative Example 1 was inferior in abrasion resistance and quality because it did not contain a thermoplastic resin having a polar functional group.

[0052] Examples 5 to 7 Spun yarns were produced in the same manner as in Example 2, except that the island component was changed to polyethylene terephthalate in Example 5, to polyethylene terephthalate copolymerized with 25 mol % of isophthalic acid and 10 mol % of adipic acid in Example 6, and to nylon 6 in Example 7.

[0053] The evaluation results of the fiber properties and fabric properties of the obtained spun yarn are shown in Table 1.

[0054] Examples 8 and 9, Comparative Examples 2 and 3 Spun yarns were produced in the same manner as in Example 2, except that the fiber length was changed as shown in Table 2.

[0055] The evaluation results of the fiber properties and fabric properties of the obtained spun yarn are shown in Table 2. Comparative Example 2 had poor abrasion resistance and poor quality due to the short fiber length. Comparative Example 3 had poor processability due to the long fiber length, and although it had excellent abrasion resistance, it was poor in quality.

[0056] Example 10, Comparative Examples 4 and 5 Spun yarns were produced in the same manner as in Example 2, except that the single fiber fineness was changed as shown in Table 2.

[0057] The evaluation results of the fiber properties and fabric properties of the obtained spun yarns are shown in Table 2. Comparative Example 4 was poor in both abrasion resistance and quality due to a small single fiber fineness. Comparative Example 5 was poor in processability due to a large single fiber fineness, and although it was excellent in abrasion resistance, it was poor in quality.

[0058] (Example 11) The spun yarn obtained in Example 2 was used as the yarn type (1) and wool having the specifications shown in Table 3 was used as the yarn type (2), and each sliver was blended in the weight ratio shown in Table 3 to obtain a spun yarn.

[0059] The evaluation results of the fabric properties of the obtained spun yarn are shown in Table 3. The fabric was excellent in quality, with good heat retention and light weight.

[0060] Examples 12 and 13 Spun yarns were prepared in the same manner as in Example 11, except that the blending ratio was changed as shown in Table 3.

[0061] The evaluation results of the fabric properties of the obtained spun yarn are shown in Table 3. Example 12, which had a high blend ratio of polypropylene staple fiber of the present invention, produced a fabric with excellent lightness, while Example 13, which had a high blend ratio of wool, produced a fabric with excellent heat retention.

[0062] Example 14 A spun yarn was produced in the same manner as in Example 11, except that the yarn type (2) was changed as shown in Table 3.

[0063] The evaluation results of the fabric properties of the obtained spun yarn are shown in Table 3. The blend of polypropylene staple fiber and cotton of the present invention also produced a fabric of good quality.

[0064] Comparative Example 6 A spun yarn was produced in the same manner as in Example 11, except that the yarn type (1) was changed as shown in Table 3.

[0065] The evaluation results of the fabric properties of the obtained spun yarn are shown in Table 3. Since yarn type (1) did not contain a thermoplastic resin having a polar functional group, the fabric had poor abrasion resistance.

[0066]

[0067]

[0068]

[0069] The polypropylene staple fibers of the present invention have improved abrasion resistance while retaining the properties of polypropylene, and have an excellent texture, and are suitable for use in fiber structures.

Claims

1. The polypropylene staple fiber is a polymer alloy staple fiber having an island-sea structure in which polypropylene (A) is a sea component and thermoplastic resin (B) having a polar functional group is an island component, the thermoplastic resin (B) having a polar functional group being exposed on the surface, the fiber length being 20 to 100 mm, and the single fiber fineness being 0.5 to 3.5 dtex.

2. 2. The polypropylene staple fiber according to claim 1, wherein the thermoplastic resin (B) having a polar functional group is a polyester.

3. The polypropylene short fibers according to claim 1 or 2, further comprising a compatibilizer (C).

4. A spun yarn comprising 20 to 80% by weight of the polypropylene short fibers according to claim 1 or 2.