Polyester short fiber

Abstract

To provide a short fiber, which is a polyester fiber with excellent moisture absorption, provides a bulky feeling when used as an inner cotton, provides a swelling feeling, firmness, and stiffness when used as a spun yarn, exhibits extremely improved resistance to cracks generated on the fiber surface by distributing stress associated with volume swelling of the fiber due to moisture absorption and / or water absorption, and has excellent process-passing property during the production of the short fiber.SOLUTION: The short fiber is a polyester sea-island composite fiber composed of at least two types of polymers, characterized in that a moisture absorption / release parameter (ΔMR) is 2.0% or more, the number of island portions in a fiber cross section is two or more, the fiber length is 20 to 100 mm, and the single fiber fineness is 1.0 to 10.0 dtex.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a hygroscopic polyester staple fiber.

Background Art

[0002] As people desire a more comfortable life, the requirements for fiber materials are also becoming more advanced, and the upgrading of fiber materials for further comfort improvement is actively carried out.

[0003] Generally, the comfort in clothing applications varies depending on the environment and atmosphere in which the material is used. Among these, maintaining the environment in the space between the clothes and the skin, that is, the environment in the clothing interior space, in an appropriate state is considered an important factor directly related to the comfort of the wearer. In this clothing interior space environment, factors affecting people's comfort include the temperature and humidity inside the clothes. However, the range of temperature and humidity inside the clothes in which people can feel comfortable is limited.

[0004] When moving from the outdoor environment to an indoor environment where the temperature is adjusted, etc., sweating occurs due to the sudden change in the atmosphere, and the comfort may be impaired by a stuffy feeling or stickiness regardless of the season. Therefore, it is required of clothing materials used near the skin surface that they can adjust the temperature and humidity inside the clothes to a comfortable range even when a sudden change in the atmosphere occurs.

[0005] For example, when moving from the outdoors to an air-conditioned indoor environment in a low-temperature environment in winter, sweating occurs inside the clothes due to the sudden rise in the atmospheric temperature, which may result in a stuffy feeling or stickiness and impair the comfort. Also, when moving from indoors to outdoors, the sweat generated indoors suddenly cools due to the outside air, causing the wearer to feel a strong chill and impairing the comfort. That is, there is a need for a material that eliminates the discomfort caused by this sweating and keeps the humidity change inside the clothes constant.

[0006] As winter clothing, there is thermal insulation clothing represented by down jackets and the like. As a heat insulation material responsible for the thermal insulation function, in addition to down and feathers, batting made of polyester fibers is increasingly being used. However, the batting made of polyester fibers has no hygroscopicity and cannot adjust the in-clothing environment, so there are cases where comfort is impaired as described above.

[0007] Therefore, in order to impart hygroscopicity to the batting made of polyester fibers, a method has been proposed in which the staple fibers that are the raw material of the batting are made into conjugate fibers with a polymer having hygroscopicity.

[0008] For example, in Patent Document 1, hygroscopic conjugate staple fibers for stuffing are proposed, which have a hygroscopic polymer as the core component and polyester as the sheath component.

[0009] In Patent Document 2, staple fibers for polyester stuffing are proposed, in which a hydrophilic compound is copolymerized and a copolymerized polyester containing at least one of a polar group-containing compound and a crosslinking agent is compounded or blended.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0011] The staple fibers disclosed in Patent Document 1 and Patent Document 2 are core-sheath conjugate fibers in which a hygroscopic polymer is arranged as the core component. However, since the hygroscopic polymer has poor mechanical properties, there are cases where the core component is absent in the fiber cross-section, that is, it exhibits characteristics similar to those of a fiber having a hollow part.

[0012] In this case, since the cross-sectional second moment of the short fibers is small, the short fibers are prone to bending. When such short fibers are used as raw cotton to make intermediate cotton, there is a problem that they are prone to sagging and do not have a bulky feeling. Similarly, even when made into spun yarns, due to their ease of bending, there is also a problem that the bulging feeling, stiffness, and firmness are weakened. Furthermore, in the liquid bath treatment during the production of short fibers, stress is generated with the volume swelling of the hygroscopic polymer in the core component, and cracks such as cracks are generated on the fiber surface due to this stress, resulting in problems such as a decrease in hygroscopicity due to the elution of the hygroscopic polymer and a decrease in the passability of the manufacturing process.

[0013] The present invention aims to solve the above problems, and provides a polyester fiber excellent in hygroscopicity. When used as intermediate cotton, it has a bulky feeling, and when made into spun yarns, it has a bulging feeling, stiffness, and firmness. By dispersing the stress generated with the volume swelling of the fiber during moisture absorption and / or water absorption, the cracks generated on the fiber surface are remarkably improved, and the short fiber is excellent in the passability of the process during the production of short fibers.

Means for Solving the Problems

[0014] In order to solve the above problems, the present invention has the following configuration. (1) A polyester sea-island composite fiber composed of at least two or more polymers, having a moisture absorption and desorption parameter ΔMR of 2.0% or more, the number of island parts in the fiber cross-section being 2 or more, the fiber length being 20 to 100 mm, and the single fiber fineness being 1.0 to 10.0 dtex, characterized short fiber. (2) The short fiber according to (1) above, characterized in that the intermediate stress elongation in the tensile test is 10% or less. (3) Granulated cotton containing a part of the short fiber according to (1) or (2) above.

Effects of the Invention

[0015] Since the short fibers of the present invention are composed of polyester, when used as the filling cotton of a stuffing, bulkiness for ensuring heat retention can be obtained. Furthermore, when made into spun yarns, sufficient swelling, stiffness, and firmness can be obtained, and the short fibers have excellent moisture absorption and desorption performance suitable for conditioning the environment inside clothes. Also, by dispersing the stress during fiber volume swelling during water absorption and / or moisture absorption, cracking on the fiber surface is suppressed, so short fibers with excellent process passability during short fiber production can be obtained.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0017] The short fibers of the present invention are polyester sea-island composite fibers composed of at least two or more types of polymers, and it is an important requirement that they have excellent hygroscopicity with a moisture absorption and desorption parameter ΔMR of 2.0% or more. Due to this property, it becomes a fiber structure that conditions the surrounding environment and suppresses stuffiness and the like accompanying sudden changes such as outside air.

[0018] The short fibers of the present invention have a moisture absorption and desorption parameter ΔMR, which is an index of hygroscopicity, of 2.0% or more as described above. ΔMR is the difference in the moisture absorption rate of the fiber at high temperature and high humidity represented by a temperature of 30°C and a relative humidity of 90%, and the standard temperature and humidity conditions represented by a temperature of 20°C and a relative humidity of 65%. The higher ΔMR is, the higher the hygroscopicity of the fiber. The measurement method is as described in the Examples section.

[0019] If ΔMR is 2.0% or more, there is less stuffiness inside clothes made of the staple fibers of the present invention, and wearing comfort is exhibited. A more preferable range of ΔMR is 3.0% or more. In this case, since a large amount of moisture can be retained in the fibers, in addition to suppressing stuffiness, for example, excellent antistatic properties are also exhibited. An even more preferable range of ΔMR is 4.0% or more. Since even more moisture can be retained in the fibers, the fibers can quickly absorb water vapor, and in addition to the summer environment, stuffiness and stickiness can be suppressed even in the winter environment.

[0020] There is no particular upper limit to the range of ΔMR, but the level achievable in the present invention is about 10%, which is the substantial upper limit. Further, the staple fibers of the present invention satisfy the above range of ΔMR before and after heat treatment or the like in the manufacturing process of batting or spun yarn.

[0021] Moisture-absorbing fibers take in water molecules by physical adsorption and / or the formation of an interaction between a functional group in the molecular structure of the polymer constituting the fiber and water molecules. In particular, when having high moisture absorbency, since a large number of water molecules are taken into the fiber, the fiber structure is loose, the rigidity of the fiber is low, and deformation is likely to occur when the fiber is stretched or bent. When such staple fibers are used to make batting or spun yarn, a bulky feeling may not be obtained, and the texture may be soft and lacking in firmness and stiffness.

[0022] The object of the staple fibers of the present invention is to obtain sufficient bulkiness to ensure heat retention when made into batting, and also to obtain a swelling feeling, firmness, and stiffness when made into spun yarn. It is important that the staple fibers are sea-island composite fibers having 2 or more island parts in the fiber cross-section.

[0023] The sea-island composite fiber referred to here has a cross-sectional shape with components arranged inside the fiber in the fiber cross-section, and the components arranged inside the fiber are the island parts. The staple fibers of the present invention have two or more island parts in the fiber cross-section, so that the rigidity of the staple fibers increases and the deformation during stretching or bending decreases. Therefore, when the staple fibers of the present invention are used to make batting or spun yarn, a bulky, firm and resilient texture can be obtained. The greater the number of island parts in the fiber cross-section, the greater the second moment of the cross-section and the increase in bending rigidity, so that an excellent bulky feeling can be obtained when made into batting. From this perspective, the number of island parts in the fiber cross-section is preferably 3 or more, more preferably 4 or more.

[0024] As an example of the method for observing the fiber cross-section in the present invention, there is a method of embedding a fiber sample with an embedding agent such as epoxy resin and taking an image at a magnification at which 10 or more single fibers can be observed with a scanning electron microscope (SEM) manufactured by HITACHI in the fiber cross-section perpendicular to the fiber axis.

[0025] It is preferable that the figure obtained by connecting the centers of gravity of the island parts arranged on the outermost periphery in the fiber cross-section of the staple fibers of the present invention with line segments is a regular polygon having the center of gravity as a vertex. The figure obtained by connecting the centers of gravity of the island parts arranged on the outermost periphery in the fiber cross-section means that when connecting the centers of gravity of the island parts with line segments, the centers of gravity are selected and depicted so that the line segments do not intersect at points other than the centers of gravity as shown in Fig. 1(a). On the other hand, when connecting the centers of gravity of the island parts with line segments as shown in Fig. 1(b), the line segments intersect at parts other than the centers of gravity of the island parts, and the figure depicted at this time is not included in the figure obtained by connecting the centers of gravity of the island parts arranged on the outermost periphery in the present invention with line segments. Also, as shown in Fig. 1(c), in the island part 2f, since other island parts (2a, 2b, 2c, 2d, 2e) are arranged between the island part and the fiber surface, the island part 2f is not included in the island parts arranged on the outermost periphery in the fiber cross-section.

[0026] In the short fibers of the present invention, a regular polygon means a figure composed of n line segments, which is an n-sided polygon. The ratios of the lengths A1, A2, A3 ··· An of each line segment to the average value Lx of these lengths (A1 / Lx, A2 / Lx, A3 / Lx ··· An / Lx) are rounded to the third decimal place, and all of them are figures with values between 0.97 and 1.03.

[0027] In the short fibers of the present invention, the figure obtained by connecting the centers of gravity of the island parts arranged on the outermost periphery in the fiber cross-section with line segments is a regular polygon with the center of gravity as the vertex. Therefore, when the fiber is bent, the change in the section modulus due to the bending direction is small, so the change in the bending stress is small depending on the bending direction of the fiber. When the short fibers of the present invention are used as batting or spun yarn, a bulky, firm, and resilient texture can be obtained. Also, when the short fibers of the present invention swell in volume due to moisture absorption, the vectors of the stresses generated are exactly opposite between adjacent island parts, and the stresses cancel each other out between the island parts. Therefore, the stress propagated to the sea part on the fiber surface side can be reduced. Since the stress propagated to the sea part on the fiber surface side is reduced, the fiber surface is less likely to crack, and the process passability is good when manufacturing batting or spun yarn using the short fibers of the present invention.

[0028] For the short fibers of the present invention, it is preferable that the ratio L / R of the radius L (μm) of the circumscribed circle including all the island parts arranged on the outermost periphery in the fiber cross-section to the fiber radius R (μm) is 0.5 to 0.9.

[0029] L / R represents the distance between the fiber surface and the island part arranged on the outermost periphery in the fiber cross-section. Even when the number of island parts is 2 or more like the short fibers of the present invention, if the island parts gather at the fiber center, it shows a pseudo single island, that is, a behavior similar to a core-sheath composite cross-section, and the rigidity of the fiber decreases. When L / R is 0.50 or more, the rigidity of the short fiber increases and the deformation during tension or bending decreases. Therefore, when the short fiber of the present invention is used to make batting or spun yarn, a bulky feeling, firmness, and a texture with a sense of stiffness can be obtained. Based on this idea, it is more preferably 0.80 or less, and even more preferably 0.60 or less. Also, when L / R is 0.5 or more, sea part cracking due to stress generated by volume swelling during moisture absorption can be suppressed, and the process passability during short fiber production becomes good.

[0030] The composite ratio of the sea part / island part of the short fiber of the present invention is preferably 50 / 50 to 90 / 10 by weight ratio. If the composite ratio of the sea part is 50% by weight or more, the decrease in the rigidity of the short fiber due to the island part can be reduced. When the short fiber of the present invention is used as batting, a bulky feeling can be obtained, and when it is used as spun yarn, a texture with firmness and a sense of stiffness can be obtained. More preferably, it is 60% by weight or more, and even more preferably 70% by weight or more. On the other hand, if the composite ratio of the sea part of the short fiber is 90% by weight or less, that is, the composite ratio of the island part is 10% by weight or more, sea part cracking due to stress generated by volume swelling when the short fiber of the present invention absorbs moisture can be suppressed, and the process passability during short fiber production becomes good. Based on this idea, it is more preferably 85% by weight or less, and even more preferably 80% by weight or less.

[0031] The short fiber of the present invention is a polyester sea-island composite fiber composed of at least two or more types of polymers. The polyester sea-island composite fiber referred to here means that among the polymers constituting the fiber, one type is polyester. That is, the polyester forms the sea component or the island component, and at least one type of other polymer forms the other component.

[0032] The polyester in the staple fibers of the present invention includes aromatic polyesters typified by polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, etc., and aliphatic polyesters typified by polylactic acid. Generally, from the viewpoints of mechanical properties, heat resistance, and handleability during production, it is preferable to use aromatic polyesters.

[0033] The above-mentioned aromatic polyester is a high molecular weight polymer having repeating units linked via ester bonds in the main chain composed of a combination of an aromatic dicarboxylic acid and an aliphatic diol, an aliphatic dicarboxylic acid and an aromatic diol, or an aromatic dicarboxylic acid and an aromatic diol. Preferably, it is an aromatic polyester composed of an aromatic dicarboxylic acid and an aliphatic diol. Examples of such aromatic dicarboxylic acids include, but are not limited to, terephthalic acid, isophthalic acid, 5-sodium sulfoisophthalic acid, 2,6-naphthalenedicarboxylic acid, etc. Examples of such aliphatic diols include, but are not limited to, ethylene glycol, 1,3-propanediol, 1,4-butanediol, cyclohexanediol, diethylene glycol, hexamethylene glycol, neopentyl glycol, etc.

[0034] When using an aromatic polyester in the staple fibers of the present invention, since the rigidity of the fibers increases as a characteristic, a bulky feeling can be obtained when using the staple fibers of the present invention as batting, and a texture with stiffness and firmness can be obtained when made into a spun yarn.

[0035] The polyester in the staple fibers of the present invention generally does not have functional groups that form strong interactions with water molecules in the polymer structure. Therefore, as examples of the method for making the ΔMR of the staple fibers of the present invention within the above range, adding a hygroscopic compound, compounding a polymer having high hygroscopicity (hereinafter sometimes referred to as a hygroscopic polymer), treating the polymer molecules on the fiber surface with ozone, etc. to generate hygroscopic functional groups, etc. can be mentioned. Among these, assuming that staple fibers having excellent hygroscopicity are to be obtained, it is preferable to compound a hygroscopic polymer to form a sea-island composite fiber.

[0036] Examples of suitable hygroscopic polymers used in the short fibers of the present invention include polyether esters, polyether amides, polyether ester amides, polyamides, thermoplastic cellulose derivatives, polyvinyl pyrrolidone, and the like. Among these, polyether esters containing polyether as a copolymer component are excellent in stability during melt molding, have high target hygroscopicity, and are preferably used for the short fibers of the present invention.

[0037] A polyether ester is a block copolymer having an ester bond and an ether bond in its polymer structure. Specifically, it is a block copolymer polymer obtained by subjecting a polyester-forming component composed of a dicarboxylic acid and a diol and a polyalkylene glycol component to a polycondensation reaction. The combination of the polyester-forming component and the polyalkylene glycol component is not limited, but as a preferred example, from the viewpoint of the heat resistance of the hygroscopic polymer, an aromatic polyester composed of an aromatic dicarboxylic acid and an aliphatic diol is used as the polyester-forming component, and a polyether ester copolymerized with polyethylene glycol can be mentioned. More preferably, it is a polyether ester composed of polybutylene terephthalate and polyethylene glycol, which is excellent in crystallinity because elution of the hygroscopic polymer into hot water can be suppressed.

[0038] The above-mentioned hygroscopic polymer has a high affinity for water and is likely to elute when it comes into contact with hot water or the like during the production of short fibers, medium-length fibers, or spun yarns. When the hygroscopic polymer elutes outside the fiber, the hygroscopicity of the fiber may decrease. Therefore, when using a hygroscopic polymer in the short fibers of the present invention, it is preferably arranged as the island component. On the other hand, generally, the molecular structure of the hygroscopic polymer is looser than that of polyester and its mechanical properties are poor. Therefore, when the hygroscopic polymer is arranged as the island component, in the fiber cross-section, the island component may be absent, that is, it may exhibit properties similar to those of a fiber having a hollow part, and particularly, the bending rigidity is likely to be small. Therefore, by adopting the composite cross-sectional form of the short fibers of the present invention, even if the hygroscopic polymer is arranged as the island component, the effect of increasing the rigidity of the fiber is remarkably exhibited. When using the short fibers of the present invention to make medium-length fibers or spun yarns, a bulky, firm, and resilient texture can be obtained.

[0039] The manufacturing method of the polymer in the present invention is not limited. When the raw materials during manufacturing are taken as monomers, the monomers may be synthesized and manufactured by general polycondensation reactions, addition polymerization reactions, etc. The monomers are not limited to petroleum-derived monomers, biomass-derived monomers, mixtures of petroleum-derived monomers and biomass-derived monomers, recycled monomers obtained by reusing polymers through chemical recycling techniques, etc. Alternatively, polymers may be manufactured from waste materials such as waste plastics by means of material recycling techniques. Also, in the polymer of the present invention, within the scope not departing from the object of the present invention, a second or third component may be copolymerized or mixed in addition to the main component.

[0040] The cross-sectional shape of the short fibers of the present invention can adopt various cross-sectional shapes such as not only round cross-sections but also flat, Y-shaped, T-shaped, field-shaped, well-shaped, etc. However, in view of the object of the present invention, in order not to reduce the second moment of cross-section, a cross-sectional shape without a hollow hole is preferred.

[0041] The fineness of the staple fiber of the present invention is 1.0 dtex or more and 10.0 dtex or less. If the fineness of the single fiber is 1.0 dtex or more, the rigidity of the fiber becomes high, and when the staple fiber of the present invention is used to form batting or spun yarn, a bulky, firm, and resilient texture can be obtained. Preferably it is 2.0 dtex or more, particularly when the form of the batting is granular batting, more preferably 3.0 dtex or more. On the other hand, if the fineness of the single fiber is 10.0 dtex or less, the fiber does not become too hard, and the processability during manufacturing of batting or spun yarn using the staple fiber of the present invention is good. Preferably it is 9.0 dtex or less, more preferably 8.0 dtex or less. When the form of the batting is granular batting, it is even more preferably 5.0 dtex or less.

[0042] The fiber length of the staple fiber of the present invention is 20 mm or more and 100 mm or less. If the fiber length is 20 mm or more, when manufacturing batting or spun yarn using the staple fiber of the present invention, entanglement between the staple fibers occurs, and stable batting and spun yarn can be obtained. When the form of the batting is granular batting, preferably it is 25 mm or more, more preferably 30 mm or more. On the other hand, if the fiber length is 100 mm or less, the bending moment does not become too large, and it is less likely to sag when made into batting or spun yarn using the staple fiber of the present invention. Preferably it is 90 mm or less, more preferably 80 mm or less. When the form of the batting is granular batting, it is even more preferably 60 mm or less.

[0043] The tensile strength of the staple fiber of the present invention is preferably 1.5 cN / dtex or more from the viewpoint of processability, but it can be used without problems even if it is 1.5 cN / dtex or less by taking measures such as using it in combination with other fibers during processing. Also, the elongation can be appropriately set according to the application, but from the viewpoint of processability, it is preferably 25% or more and 60% or less.

[0044] In the tensile test of the staple fibers of the present invention, the intermediate stress elongation is preferably 10% or less. The intermediate stress elongation in the tensile test referred to herein is the elongation when measuring the tensile strength by the tensile test in the method described in Paragraph 8.7 of JIS L1015:2010 (Test Methods for Chemical Fiber Staples) and showing the stress half of the measured tensile strength. If the intermediate stress elongation in the tensile test is 10% or less, the fiber has high rigidity, and when the staple fibers of the present invention are used as batting or spun yarn, a bulky, firm, and resilient texture can be obtained. More preferably, it is 8% or less. Since the fiber is less likely to be deformed by an external force, the process passability is good when manufacturing batting or spun yarn. Even more preferably, it is 6% or less.

[0045] The crimp number of the staple fibers of the present invention is preferably 5 crests / 25 mm or more and 35 crests / 25 mm or less. If the crimp number is 5 crests / 25 mm or more, in addition to the rigidity of the staple fibers, a bulky feeling due to the crimp can be obtained. Therefore, when the staple fibers of the present invention are used as batting or spun yarn, a bulky, firm, and resilient texture can be obtained. Also, if the crimp number is 35 crests / 25 mm or less, the staple fibers are likely to be entangled with each other, and the process passability when manufacturing batting or spun yarn is good.

[0046] The staple fibers of the present invention can be obtained by known melt spinning and composite spinning techniques, and are exemplified as follows. However, the spinning method and composite method are not limited to those exemplified here.

[0047] As a method for producing the staple fibers of the present invention composed of two or more types of polymers, it is also possible to produce them by a melt spinning method, a solution spinning method such as a wet method and a dry-wet method, etc., for the purpose of manufacturing staple fibers. From the viewpoint of enhancing productivity, the melt spinning method is preferable. Also, in the melt spinning method, it is preferable to use a composite die described later. When using the melt spinning method, regarding the spinning temperature at that time, it is set to the temperature at which mainly the high melting point or high viscosity polymer shows fluidity among the polymer types used. This temperature at which fluidity is shown varies depending on the molecular weight, but it can be stably manufactured by setting it between the melting point of the polymer and the melting point + 60°C.

[0048] As a manufacturing method by the melt spinning method, for example, the polymer of the sea part and the polymer of the island part are melted separately, metered and transported by a gear pump, and a composite flow is formed in the normal way so as to have a specific composite structure and discharged from a spinneret, and the yarn is cooled to room temperature by blowing cooling air with a yarn cooling device such as a chimney. It may be a two-step method in which the cooled yarn is oiled by an oiling device, taken up by a take-up roller, wound once as an undrawn yarn by a winder (winding device), and then drawn in another process, or it may be a one-step method in which after being taken up by a take-up roller, it is drawn by passing through draw rollers with different peripheral speeds and then wound by a winder. Next, mechanical crimping is imparted to the obtained drawn yarn, and finally it is cut to a predetermined fiber length to obtain the short fiber of the present invention.

[0049] In the short fiber of the present invention, it is preferable to make the melt viscosity ratio of two or more kinds of polymers used in the sea part and the island part less than 5.0, because a composite polymer flow can be stably formed and fibers with a good composite cross section can be obtained.

[0050] As the composite spinneret used when manufacturing the short fiber of the present invention, it is preferable to use the composite spinneret described in JP-A-2011-208313. The composite spinneret shown in FIG. 2 is incorporated into a spinning pack in a state where three large types of members, namely a metering plate 8, a distribution plate 9, and a discharge plate 10, are laminated from above and used for spinning. Incidentally, FIG. 2 is an example using two kinds of polymers such as polymer A and polymer B. In a conventional composite spinneret, it is difficult to control the shape of the island part as described above, and it is preferable to use a composite spinneret that utilizes a fine flow path as exemplified in FIG. 2.

[0051] In the spinneret member exemplified in FIG. 2, the metering plate 8 measures the amount of polymer per each discharge hole and each distribution hole and flows in, the distribution plate 9 controls the composite cross section and its cross-sectional shape in the cross section of the single fiber, and the discharge plate 10 compresses and discharges the composite polymer flow formed by the distribution plate 9.

[0052] To avoid complication in the description of the composite die, although not shown in the figures, for the members laminated above the metering plate 8, members with formed flow paths can be used according to the spinning machine and the spin pack. By designing the metering plate 8 to match the existing flow path members, the existing spin pack and its members can be utilized as they are, so there is no need to specifically dedicate a spinning machine for this die. Also, multiple flow path plates can be laminated between the flow path and the metering plate 8 or between the metering plate 8 and the distribution plate 9. Thereby, a configuration can be achieved in which a flow path for efficiently transferring the polymer is provided in the die cross-section direction and the cross-section direction of the single fiber, and the polymer is introduced into the distribution plate 9. The composite polymer stream discharged from the discharge plate 10 is cooled and solidified according to the above manufacturing method, an oil agent is applied, and then taken up by a roller having a specified peripheral speed, whereby fibers having a desired composite cross-section can be obtained.

[0053] In the production of the short fibers of the present invention, the spinning draft represented by the speed ratio between the die discharge linear speed and the take-up roller is preferably 10 or more and less than 300. Here, the die discharge linear speed is the discharge volume per unit time of the polymer discharged from the discharge holes of the spinning die divided by the cross-sectional area of the die discharge holes. This spinning draft is correlated with the orientation of the fibers that occurs from when they are discharged from the discharge holes of the spinning die until they are cooled and taken up by the take-up roller. The greater the spinning draft, the greater the orientation of the fibers until they are taken up by the take-up roller. By setting the spinning draft within such a range, short fibers having excellent mechanical properties and excellent hygroscopicity can be obtained. When the spinning draft is 300 or more, the orientation of the fibers progresses and crystallization proceeds before they are taken up by the take-up roller, so the hygroscopicity decreases. Also, since the draw ratio in the drawing after the take-up roller becomes small, the intermediate stress elongation becomes large, and when using the short fibers of the present invention as carded cotton or spun yarn, it becomes bulky and lacks texture. On the other hand, when the spinning draft is less than 10, since the spinning draft is too low, the tension applied to the polymer immediately after discharge from the die is low, causing yarn vibration and the like, resulting in a decrease in productivity such as yarn breakage and a decrease in the quality of short fibers due to uneven thickness. More preferably, it is 30 or more and less than 200.

[0054] When manufacturing the short fibers of the present invention, the direction of the cooling air blown by a yarn cooling device such as a chimney may be from a single direction or in an annular direction with respect to the yarn, and the speed of the cooling air is preferably 10 m / min or more and 50 m / min or less. If the speed of the cooling air is 10 m / min or more, the yarn is sufficiently cooled, so there is little unevenness in the structure in the fiber longitudinal direction, and the quality of the obtained short fibers is excellent, which is preferable. More preferably, it is 15 m / min or more. On the other hand, if the speed of the cooling air is 50 m / min or less, the difference in the cooling rate between the yarn close to the cooling air outlet and the yarn far from it becomes small, and asymmetric cooling does not occur, so the bending rigidity of the short fibers increases, which is preferable. More preferably, it is 40 m / min or less.

[0055] As a method of stretching the short fibers of the present invention, it may be single-stage stretching or multi-stage stretching, and the stretching temperature can be appropriately selected according to the type of polymer used. The method of heating the yarn during stretching can also be adopted by any method such as a hot roller, a hot pin, steam, a liquid bath, etc. due to the effect of increasing the stability of the fibers due to the composite cross-sectional form of the short fibers of the present invention.

[0056] Examples of the method of imparting mechanical crimp to the short fibers of the present invention include the stuffing box method, the push-in heating gear method, the high-speed air injection push-in method, etc. The stuffing box method is preferable because of the ease of adjusting the crimp degree. In the stuffing box method, the crimp degree can be adjusted by adjusting the stuffing pressure in the crimper box or the yarn temperature when entering the crimper box.

[0057] When using the short fibers of the present invention to make batting or spun yarn, other fibers can be included without departing from the object of the present invention. The other fibers are not particularly limited, such as natural fibers, synthetic fibers, and regenerated fibers, but polyester fibers are preferable because a bulky feeling, firmness, and a texture with a sense of stiffness can be obtained when made into batting or spun yarn.

[0058] When using the short fibers of the present invention to make intermediate cotton, there is no limitation on its form. In addition to the above-mentioned granular cotton, for example, webs, non-woven sheet cotton, and shredded cotton can be mentioned. As a method for manufacturing intermediate cotton, the short fibers of the present invention are passed through a carding machine to make opened fibers. When other fibers are included, opened fibers made of other fibers are added to the opened fibers made of the short fibers of the present invention, and they are stirred and mixed with a blower or the like to make mixed cotton. When the form is granular cotton, the opened fibers and / or the mixed cotton are put into a balling machine to make granular cotton. In the case of non-woven sheet cotton, after webs made of opened fibers and / or mixed cotton are stacked in a sheet shape, a chemical bond in which a resin is sprayed to bond the fibers together, a thermal bond in which low-melting binder fibers are also mixed when making mixed cotton and the binder fibers are melted by heat to bond, a needle punch in which the stacked webs in a sheet shape are penetrated with needles to entangle the fibers together, a spunlace in which the fibers are entangled with each other by a water stream instead of needles, etc. can be mentioned, but it is not limited thereto.

[0059] When using the short fibers of the present invention to make granular cotton, the diameter is preferably 1 mm or more and 30 mm or less. If the diameter of the granular cotton is 1 mm or more, it is preferable because it has excellent bulkiness. More preferably, it is 10 mm or more. On the other hand, if the diameter of the granular cotton is 30 mm or less, it is preferable because the form of the granular cotton is stable. More preferably, it is 20 mm or less.

[0060] When using the short fibers of the present invention to make spun yarn, there is no limitation on its form, and single yarn, ply yarn, multi-fold yarn, etc. can be mentioned. There is also no limitation on the twist of the spun yarn, but from the viewpoints of the strength and bulkiness of the spun yarn, the twist coefficient, which is the strength of the twist, is preferably 2.0 or more and 6.0 or less. There is also no limitation on the manufacturing method of the spun yarn, and known methods such as cotton spinning, wool spinning, and bast fiber spinning can be adopted.

[0061] The short fibers of the present invention, the intermediate cotton and the spun yarn made of the short fibers of the present invention are excellent in hygroscopicity, and thus can be suitably used in applications where comfort and quality are required. For example, general clothing applications, sports clothing applications, bedding applications, interior applications, material applications, etc. can be mentioned, but it is not limited thereto.

Examples

[0062] The present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. Each characteristic value in the examples was measured using the following methods.

[0063] A. Melt viscosity of polymer For a polymer sample with a moisture content of 300 ppm or less by a vacuum dryer, using a Capillograph manufactured by Toyo Seiki, the sample was put into a heating furnace set at the same temperature as the spinning temperature, melted in a nitrogen atmosphere, the strain rate was changed stepwise, and the sample was extruded from the capillary at the tip of the heating furnace to measure the viscosity. After the sample was put into the heating furnace and retained for 5 minutes, the measurement was started, and the value at a shear rate of 1216 sec -1 was taken as the melt viscosity of the polymer.

[0064] B. Melting point (Tm) of polymer Using a differential scanning calorimeter (DSC) Q2000 type manufactured by TA instruments, 20 mg of a polymer sample was heated from 20°C to 300°C at a heating rate of 20°C / min, held at 300°C for 5 minutes, then cooled from 300°C to 20°C at a cooling rate of 20°C / min, held at 20°C for 1 minute, and then heated from 20°C to 280°C at a heating rate of 20°C / min. The peak top temperature of the endothermic peak observed was taken as the melting point. When multiple endothermic peaks were observed, the endothermic peak top on the highest temperature side was taken as the melting point.

[0065] C. Fiber length It was measured by the method described in JIS L1015:2010 (Test method for chemical fiber staple).

[0066] D. Denier per filament The linear density was determined by the method described in JIS L1015:2010 (Test method for chemical fiber staple), and the denier per filament was obtained by dividing the linear density by the number of single fibers when the linear density was determined.

[0067] E. Tensile strength, elongation, and intermediate stress elongation The fiber sample was measured using "TENSILON" (registered trademark) UCT-100 manufactured by Orientec Co., Ltd. in accordance with the standard time test (constant speed elongation system) described in JIS L1015:2010 (Test Methods for Chemical Fiber Staples). The elongation at break was determined from the elongation at the point indicating the maximum strength in the tensile strength-elongation curve. The tensile strength was taken as the value obtained by dividing the maximum strength by the fineness. The intermediate stress elongation was determined from the elongation at the point indicating 50% of the maximum strength. The measurement was carried out 10 times, and the average values were taken as the tensile strength, elongation at break, and intermediate stress elongation.

[0068] F. Number of crimps It was determined by the method described in JIS L1015:2010 (Test Methods for Chemical Fiber Staples).

[0069] G. ΔMR Weigh about 1 - 2 g of the fiber sample or fabric sample into a weighing bottle, dry it at 110°C for 2 hours, and then measure the mass, which was designated as w 0 Next, after keeping the dried fiber sample at a temperature of 20°C and a relative humidity of 65% for 24 hours, measure the mass, which was designated as w 65% Then, adjust the temperature to 30°C and the relative humidity to 90%, keep the fiber sample for 24 hours, and then measure the mass, which was designated as w 90% MR 1 = [(w 65% - w 0 ) / w 0 × 100 ··· (2) MR 2 = [(w 90% - w 0 ) / w 0 × 100 ··· (3) ΔMR = MR 2 - MR 1 ··· (4) At this time, the values calculated by formulas (2) to (4) were taken as ΔMR.

[0070] H. Radius L of the circumscribed circle ​The fiber sample was embedded with an embedding agent such as epoxy resin, and an image was taken at a magnification where 10 or more single fibers could be observed with a Hitachi scanning electron microscope (SEM) for the fiber cross-section perpendicular to the fiber axis. By analyzing the obtained image using WinROOF manufactured by Mitani Corporation, a computer software, the radius of the circumscribed circle including all the island parts arranged on the outermost periphery in the fiber cross-section was measured up to the third decimal place. The simple arithmetic mean of the results obtained for 10 randomly extracted single fibers was calculated, and the value obtained by rounding off the third decimal place was taken as the radius L (μm) of the circumscribed circle.

[0071] I. Fiber radius R Similar to item I, an image of the fiber cross-section was taken with an SEM, and the radius of a single fiber randomly extracted within the same image was measured up to the third decimal place in μm units from each of the taken images. The simple arithmetic mean of the results obtained for 10 randomly extracted single fibers was calculated, and the value obtained by rounding off the third decimal place was taken as the fiber radius D (μm). Here, when the fiber cross-section perpendicular to the fiber axis was not a perfect circle, its area was measured, and the value obtained by converting it into a circle was adopted.

[0072] J. Bulky feeling The short fibers were passed through a card to produce a web with a basis weight of 60 g / m 2 and the obtained web was allowed to stand for 24 hours in an environment at room temperature of 20°C and a relative humidity of 65%. 16 g of the treated web was placed in a transparent box with a 200 mm square bottom, and then an initial load of 0.094 g / cm 2 was applied onto the web with a 200 mm square plate, and the thickness (bulkiness (mm)) of the web after 1 minute was measured. The measurement values were evaluated according to the following criteria. The average of two measurements was taken as the result. A: 65.0 mm or more B: 60.0 mm or more and less than 65.0 mm C: Less than 60.0 mm.

[0073] K. Steaming feeling The web processed in the same manner as in item J was wrapped around the dominant arms of 10 subjects. Subsequently, they were moved to an indoor environment with a temperature of 10°C and a relative humidity of 10%, assuming an outdoor winter without heating, and were made to sit on a chair and rest quietly. Ten minutes after sitting down, they were made to perform walking exercise at a speed of 100 m per minute for 30 minutes. After 30 minutes had passed, they were moved to an indoor environment with a temperature of 25°C and a relative humidity of 55%, assuming an indoor environment with heating, and were made to sit on a chair and rest quietly. At the stage when 10 minutes had passed since sitting down, regarding the state inside the web wrapped around the dominant arm, the subjects were asked to evaluate it on a scale of 5 points where "no sense of stuffiness is felt" is 5 points, "almost no sense of stuffiness is felt" is 4 points, "a slight sense of stuffiness is felt" is 3 points, "a sense of stuffiness is felt" is 2 points, and "a strong sense of stuffiness is felt" is 1 point. The simple average of the scores given by each subject was calculated, and a passing grade was set at an average score of 3.0 points or higher, and an excellent grade was set at 4.0 points or higher.

[0074] L. Bulky property Using the method described in paragraph 8.3.2 of JIS L1903:2017 (Feather Test Method), the granulated cotton produced in the examples and comparative examples was weighed and put into the measuring device. After placing the loading disk and allowing it to stand for 2 minutes, the height at which the granulated cotton inside the measuring device contacts the loading disk was read in units of 2 cm 3 / g as the bulky property (cm 3 / g).

[0075] (Example 1) Polyethylene terephthalate copolymerized with 1.5 mol% of sodium 5-sulfoisophthalate and 1.0 wt% of polyethylene glycol with a number average molecular weight of 1000 g / mol (PEG1000 manufactured by Sanyo Chemical Industries, Ltd.) (melt viscosity 170 Pa·s, melting point 244 °C) as the sea component, and polybutylene terephthalate copolymerized with 50 wt% of polyethylene glycol with a number average molecular weight of 8300 g / mol (PEG6000S manufactured by Sanyo Chemical Industries, Ltd.) (melt viscosity 50 Pa·s, melting point 217 °C) as the island component. At a spinning temperature of 285 °C, the polymers of the sea component and the island component were melted separately, then metered so that the sea / island ratio was 80 / 20 by weight, and introduced into a spinning pack incorporating the composite die shown in Figure 2. The incoming polymer was discharged from the discharge holes (hole diameter 0.30 mm, number of holes 2000) to form a sea-island composite form with 3 islands and an equilateral triangle island arrangement. While taking up the discharged composite polymer stream with the peripheral speed of the take-up roller being 1000 m / min, it was solidified with cooling air at a wind speed of 35 m / min by a cooling device, oiled with a water-containing oil agent by an oiling device, then combined with 20 other spinning bobbins through a free roller and a convergence 0.1% guide, and dropped and stored in a can to obtain an undrawn yarn. Next, while aligning 30 undrawn yarns, they were led into a warm water bath at a temperature of 90 °C, drawn at a draw ratio of 3.0 times, and the drawn yarn was led to a crimper to impart mechanical crimping to obtain a crimped tow. After drying the obtained crimped tow, a finishing oil agent was applied, and it was cut by a rotary cutter to obtain short fibers with a single fiber fineness of 3.3 dtex and a fiber length of 38 mm. The obtained short fibers were carded to open them into cotton, and this cotton was put into a balling machine to obtain granular cotton with a diameter of 10 mm. The evaluation results of the obtained short fibers and granular cotton are shown in Table 1.

[0076] (Example 2) Short fibers with a single fiber fineness of 5.0 dtex and a fiber length of 38 mm and granular cotton with a diameter of 10 mm were obtained in the same manner as in Example 1 except that the draw ratio during drawing the undrawn yarn was 2.0 times. The evaluation results of the obtained short fibers and granular cotton are shown in Table 1.

[0077] (Example 3) Except that the ratio of the Kairi / Shima part was measured so as to be 50 / 50 by weight, short fibers with a single fiber fineness of 3.3 dtex and a fiber length of 38 mm and granular cotton with a diameter of 10 mm were obtained in the same manner as in Example 1. The evaluation results of the obtained short fibers and granular cotton are shown in Table 1.

[0078] (Example 4) Polyethylene terephthalate (melt viscosity 68 Pa·s, melting point 251°C) copolymerized with 16% by weight of polyethylene glycol (PEG6000S manufactured by Sanyo Chemical Industries, Ltd.) having a number average molecular weight of 8300 g / mol was used as the sea part, and polyethylene terephthalate (melt viscosity 120 Pa·s, melting point 254°C) was used as the island part. At a spinning temperature of 285°C, the polymers of the sea part and the island part were melted separately, then measured so that the ratio of the sea part / island part was 90 / 10 by weight, and introduced into a spinning pack incorporated with the composite die shown in Figure 2. The polymer flowing in was discharged from the discharge holes (hole diameter 0.30 mm, number of holes 2000 holes) so as to form a sea-island composite form with 3 islands and an equilateral triangle island arrangement. While taking up the discharged composite polymer stream at a peripheral speed of the take-up roller of 1000 m / min, it was solidified with cooling air at a wind speed of 35 m / min by a cooling device, oiled with a water-containing oil agent by an oiling device, and then combined with 20 other spinning bobbins through a free roller with a convergence guide of 0.1%. After that, it was shaken down and stored in a can to obtain an undrawn yarn. Next, while aligning 30 undrawn yarns, they were led into a warm water bath at a temperature of 90°C and drawn at a draw ratio of 3.1 times. The drawn yarn was led to a crimper to impart mechanical crimping to obtain a crimped tow. After drying the obtained crimped tow, a finishing oil agent was applied, and it was cut by a rotary cutter to obtain short fibers with a single fiber fineness of 3.3 dtex and a fiber length of 38 mm. The obtained short fibers were passed through a card to open them into cotton, and this cotton was put into a ball machine to obtain granular cotton with a diameter of 10 mm. The evaluation results of the obtained short fibers and granular cotton are shown in Table 1.

[0079] (Example 5) After obtaining a crimped tow in the same manner as in Example 1, by adjusting the cutting conditions with a rotary cutter, short fibers with a single fiber fineness of 3.3 dtex and a fiber length of 51 mm and granular cotton were obtained. The evaluation results of the obtained short fibers and granular cotton are shown in Table 1.

[0080] (Comparative Example 1) Short fibers with a single fiber fineness of 3.3 dtex and a fiber length of 38 mm and granular cotton with a diameter of 10 mm were obtained in the same manner as in Example 1, except that the core-sheath composite form had 1 island. Since the obtained short fibers had a core-sheath composite cross-section, the bending rigidity was low, the bulky feeling was poor, and the filter power of the produced granular cotton was also small. The evaluation results are shown in Table 1.

[0081] (Comparative Example 2) Short fibers with a single fiber of 3.3 dtex and a fiber length of 120 mm and granular cotton with a diameter of 10 mm were obtained in the same manner as in Example 1, except that the cutting interval by a rotary cutter was changed. Since the fiber length of the obtained short fibers was too long, the bulky feeling was poor, and the filter power of the produced granular cotton was also small. The evaluation results are shown in Table 1.

[0082] (Comparative Example 3) Short fibers with a single fiber fineness of 3.3 dtex and a fiber length of 38 mm and granular cotton with a diameter of 10 mm were obtained in the same manner as in Example 1, except that the sea / island ratio was measured so as to be 95 / 5 by weight. The obtained short fibers had a low ΔMR and a stuffy feeling. The evaluation results are shown in Table 1.

[0083]

Table 1

Industrial Applicability

[0084] The short fibers of the present invention are polyester fibers excellent in hygroscopicity. When used as batting, a bulky feeling can be obtained, and when used as spun yarn, a swelling feeling, firmness, and stiffness can be obtained. Further, by dispersing the stress generated due to the volume swelling of the fiber during moisture absorption and / or water absorption, the cracks generated on the fiber surface are remarkably improved, and the process passability during short fiber production is also excellent.

Explanation of Signs

[0085] 1 Sea part 2a, 2b, 2c, 2d, 2e, 2f Island part A line segment connecting the intersections (centroids) of any two straight lines that bisect the area of adjacent island parts among the island parts arranged on the outermost periphery of the cross-sections of the 3a, 3b, and 3c fibers 4 Measuring plate 5 Distribution plate 6 Discharge plate

Claims

1. A polyester sea-island composite fiber made of at least two kinds of polymers, the staple fiber having a moisture absorption and desorption parameter ΔMR of 2.0% or more, a number of island portions in a fiber cross section of 2 or more, a fiber length of 20 to 100 mm, and a single fiber fineness of 1.0 to 10.0 dtex.

2. 2. The staple fiber according to claim 1, wherein the intermediate stress elongation in a tensile test is 10% or less.

3. 3. A granular cotton comprising, in part, the staple fiber according to claim 1 or 2.

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