polymer alloy fiber

Abstract

To provide a polymer alloy fiber that causes a functional part or a functional particle to efficiently function by distributing unevenly island components dotted in a sea component in a fiber cross-section where the sea component and the island components are separated from each other.SOLUTION: A polymer alloy fiber is configured such that in a region within 30% in a direction toward a fiber center from a fiber surface an island component diameter CV% is 50% or more in a fiber cross-section where plural polymers are separated into sea components and island components.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a polymer alloy fiber in which two or more different polymers are mixed. [Background technology]

[0002] Fibers made from thermoplastic polymers such as polyester and polyamide have excellent mechanical properties and dimensional stability, and are used in a wide range of applications, from clothing to industrial applications such as interior and vehicle interiors.As the properties required of materials become more diverse, a variety of functional fibers have been developed.

[0003] For example, there are methods for imparting softness and texture by reducing the fiber diameter, and for imparting moisture absorption and quick-drying properties or changing the appearance by changing the fiber cross section from a normal round cross section to a modified cross section. There are also methods for imparting new functionality such as anti-transparency or UV protection by making the polymer that constitutes the fiber itself contain functional particles or copolymerize other components, and methods for making composite fibers composed of two or more types of polymers.

[0004] Composite fibers can combine functions that cannot be achieved with a single polymer, and can even be endowed with completely new functions, making them a mainstream technology for achieving functional fibers.

[0005] There are two methods for manufacturing composite fibers: the polymer alloy method, in which multiple polymers are melt-mixed in a channel, and the composite spinning method, in which multiple molten polymers are metered and controlled in separate channels to form the desired fiber cross-section depending on the purpose.Of these, the polymer alloy method makes it possible to manufacture functional fibers using general-purpose spinning equipment, and is easy to adopt in developments aimed at improving the functionality of textile products, so it is being widely deployed.

[0006] There are various polymer alloy methods, such as a method of dry-blending two or more resins and melting them in a mixed state, a method of kneading the combined resins in advance using a melt extruder equipped with a kneading function, etc. In these methods, by appropriately adjusting the mixing conditions to combine two or more polymers, it is possible to produce polymer alloy fibers in which one polymer is finely dispersed as island components in the sea component that forms the matrix.

[0007] In polymer alloy fibers, by utilizing a compatibilizer or the like, which is an intermediate component of the combined polymers, island component fibers can be uniformly and finely dispersed in the sea component, thereby making it possible to eliminate defects of the sea component polymer and improve its functionality, as disclosed in Patent Document 1 or Patent Document 2.

[0008] Patent Document 1 discloses a technology for using a specific compatibilizer to mix polylactic acid and polypropylene, a combination of polymers with relatively low affinity, to obtain a composite fiber in which polypropylene forms the sea and polylactic acid forms the islands. By combining the properties of each polymer, Patent Document 1 makes it possible to achieve both heat resistance and dyeability, which had not been achieved before.

[0009] In addition, in Patent Document 2, polyolefin is melt-mixed with polyamide, and the polyolefin is finely dispersed in the polyamide matrix, thereby achieving the desired acid resistance while maintaining the hydrophilicity and dyeability that are the characteristics of polyamide fibers. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] JP 2010-15072 A (Claims) [Patent Document 2] JP 3-51314 A (Claims) Summary of the Invention [Problem to be solved by the invention]

[0011] Patent Document 1 describes a fiber cross section in which polypropylene is used as a sea component and highly heat-resistant polylactic acid as island components, with the island components uniformly dispersed, in order to improve the heat resistance of the polypropylene fiber. It also describes that the island component polylactic acid is not exposed on the fiber surface due to concerns about interfacial delamination caused by the low affinity between polypropylene and polylactic acid. However, when the bulk properties of the polymer alloy fiber are evaluated, it is true that the heat resistance is improved. However, since only the polypropylene with low heat resistance is exposed on the outermost fiber layer, when a compressive force is applied while heated, such as with an iron, or when heated as a bundle, the polypropylene on the fiber surface melts, causing the fibers to collapse or causing fusion between adjacent fibers. Therefore, it is difficult to say that practical heat resistance is imparted.

[0012] Patent Document 2 describes that the sea component is polyamide and the island component is polyolefin, and that the island component is present only in a part of the fiber surface layer, in the hope that acid resistance, which is a problem with fibers made solely of polyamide, can be imparted by dispersing and mixing polyolefin, which has high chemical resistance, in the polyamide. However, since the polyamide is exposed in the outermost layer of the fiber that substantially comes into contact with the acid solution and becomes embrittled from there, the expected level of chemical resistance may not be obtained in some cases.

[0013] Patent Documents 1 and 2 relate to polymer alloy fibers obtained by melt-mixing two types of polymers with different properties, and the technical idea is to make island component fibers finely dispersed in the sea component matrix by utilizing a compatibilizer or the like, which may give functions such as heat resistance and chemical resistance that cannot be achieved with the sea component polymer alone.

[0014] However, in Patent Documents 1 and 2, the island component fibers are basically uniformly dispersed and cannot be arbitrarily arranged in the fiber cross section, which may prevent effective utilization of the island component fibers' properties that contribute to functionalization. Therefore, in order to achieve the desired properties, it may be necessary to excessively increase the island component content. In particular, when it is important to change the properties of the outermost fiber layer to achieve the desired properties, it becomes necessary to increase the island component content in the outermost fiber layer, which naturally leads to an excessive increase in the island component content.

[0015] In this case, functional polymers (island components) are certainly arranged in the surface layer of the fiber, but the excess island components arranged in the inner layer do not exert their effects, and in terms of the entire fiber, there are many unnecessary island components. In other words, there are many unnecessary island components in the inner layer, which may deteriorate the mechanical properties, which are the basic properties of the fiber, or may not fully exhibit the properties of the required sea component polymer, and there are cases where the effects expected from the polymer alloy method are not achieved.

[0016] Furthermore, when it is necessary to increase the mixing ratio of island components more than necessary, it is necessary to highly precisely control the mixing conditions in order to suppress fluctuations in the mixing ratio over time. Also, polymer alloys in which the ratio of two types of polymers is not biased to either one often have complex rheological properties in which the fluidity of the two types of polymers exists, resulting in unstable discharge behavior when extruded from a spinneret, and sometimes resulting in a significant deterioration in spinnability.

[0017] For this reason, there has been a demand for a polymer alloy fiber in which the dispersion morphology of island components and further the arrangement thereof can be controlled. [Means for solving the problem]

[0018] The object of the present invention is achieved by the following means: (1) A polymer alloy fiber characterized in that in a fiber cross section in which a plurality of polymers are separated into a sea part and island parts, the island part diameter CV% is 50% or more in a region within 30% from the fiber surface toward the fiber center, and each island part exists discontinuously in the fiber axis direction. (2) In a fiber cross section in which multiple polymers are separated into a sea component and an island component, the ratio (A / B) of the average diameter of the island component in the region within 30% from the fiber surface toward the fiber center (A) to the average diameter of the island component in the region within 30% from the fiber center toward the fiber surface (B) is 5 or more. Each island component is discontinuous in the fiber axis direction. A polymer alloy fiber characterized by: [Effects of the Invention]

[0019] The polymer alloy fiber of the present invention is characterized in that the island components are unevenly distributed in the sea component, thereby allowing the functional components to function efficiently. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic diagram of a cross-sectional structure of a polymer alloy fiber of the present invention in which island components are induced to be unevenly distributed. [Figure 2] FIG. 1 is a diagram for understanding the "fiber surface," "fiber center," "region within 30% from the fiber surface toward the fiber center," and "region within 30% from the fiber center toward the fiber surface" in the polymer alloy fiber of the present invention. [Figure 3] 1A and 1B are diagrams showing an example of a long flow channel used in the production of the polymer alloy fiber of the present invention, in which (a) is a schematic diagram of a spinneret in which a long flow channel is installed, (b) is a schematic diagram of a long flow channel installed in the spinneret, and (c) is a schematic diagram of a cross section of the long flow channel. DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention will be described in detail below together with preferred embodiments.

[0022] It is important that in the cross section of the polymer alloy fiber of the present invention, in which a plurality of polymers are separated into a sea part and island parts, the island part diameter CV% is 50% or more in a region within 30% from the fiber surface toward the fiber center.

[0023] Within this range, it can be said that the island components are unevenly distributed in the cross section of the fiber, and the exposure of the sea component to the surface layer, which has been a drawback of conventional polymer alloy fibers, can be minimized, thereby enabling the desired functions to be efficiently exhibited.

[0024] In the cross section of the polymer alloy fiber of the present invention, it is important that the island component diameter CV% is 50% or more in a region within 30% from the fiber surface toward the fiber center. However, it is more preferable that the island component diameter CV% is less than 50% in a region within 70% from the fiber center toward the fiber surface excluding the region.

[0025] The polymer alloy fiber referred to in the present invention means that a plurality of blended polymers are separated into a sea component and island components in the fiber cross section, and each island component exists discontinuously in the fiber axial direction. The sea component and island component referred to here mean the island and sea components, respectively, of the different components separated into islands-in-a-sea form by blending. The term "island-in-a-sea form" also means that the island components are separated into a plurality of parts by the sea component.

[0026] The island component diameter CV% in the present invention is calculated by the following formula: Island component diameter CV% = (standard deviation of diameter / average diameter) × 100 (1) The standard deviation of diameters and average diameters referred to here are determined as follows. Specifically, a cross section of a single polymer alloy fiber perpendicular to the fiber axis is photographed with a transmission electron microscope (TEM) or a scanning electron microscope (SEM) at a magnification that allows observation of 150 or more island component polymers. At this time, metal staining can be applied, if necessary, to enhance the contrast between the sea component and the island component. From the two-dimensionally photographed image, image processing software (e.g., WinROOF manufactured by Mitani Shoji) is used to measure the diameters of island component polymers randomly sampled within the same image. Here, the island component polymers appearing in the fiber cross section are not necessarily perfectly circular. However, if they are not perfectly circular, their area is measured and the value obtained by converting them into a circle is used. These values ​​are measured in nm to one decimal place and rounded off. The average diameter is determined by measuring the diameters of the 150 sampled island component polymers and calculating the simple number average. The standard deviation of diameters is calculated from the diameters of the individual island component polymers and the average diameter.

[0027] In the present invention, the fiber surface means the outermost periphery in the cross section of the fiber, and the fiber center means the intersection of any two lines that divide the area of ​​the cross section of the fiber into two equal parts.

[0028] In the cross section of the polymer alloy fiber of the present invention, when the island component diameter CV% is 50% or more in a region within 30% from the fiber surface toward the fiber center, the desired function can be effectively exhibited, but to further reduce the adverse effect of the sea component present in the surface layer, the island component diameter CV% is preferably 75% or more. However, the presence of island components of various sizes may have complex rheological properties, and may significantly deteriorate spinnability, such as unstable behavior when extruded from a spinneret, so the island component diameter CV% is more preferably 100% or less.

[0029] Here, the region within 30% from the fiber surface toward the fiber center (E in Figure 2) refers to the region obtained by excluding the region from the fiber center toward 70% of the fiber surface from the entire fiber cross section, and the region from the fiber center toward 70% of the fiber surface refers to the region of the fiber cross section that has been reduced to the same fiber center and have an area ratio of 70%.

[0030] In the cross section of the polymer alloy fiber of the present invention, the ratio (A / B) of the average island component diameter (A) of the region within 30% from the fiber surface toward the fiber center to the average island component diameter (B) of the region within 30% from the fiber center toward the fiber surface is preferably 5 or more.

[0031] The values ​​of A and B are determined as follows. That is, in each region, images are taken with a transmission electron microscope (TEM) or a scanning electron microscope (SEM) at a magnification such that 150 or more island component polymers can be observed. At this time, metal staining can be performed as necessary to clarify the contrast between the sea component and the island component. From the two-dimensionally taken image, image processing software (e.g., WinROOF manufactured by Mitani Corporation) is used to measure the diameters of 150 island component polymers randomly extracted within the same image, and then the simple number average value is determined. Here, the island component polymers appearing in the fiber cross section are not necessarily perfect circles, but if they are not perfect circles, their area is measured and the value obtained by converting them into circles is used.

[0032] Here, the region within 30% from the fiber center in the fiber surface direction (F in FIG. 2) means a region that is reduced to the same fiber center and has an area ratio of 30% relative to the fiber cross section.

[0033] When the A / B value is 5 or greater, even if the fiber has a very large dispersion structure near the fiber surface, the island component fibers near the fiber center have a fine dispersion structure, which suppresses unstable elongation deformation behavior due to the complex rheological properties specific to polymer alloys and leads to stabilization of spinnability. Furthermore, suppressing unstable elongation deformation behavior also has the effect of minimizing excessive thickness unevenness in the fiber axis direction of the resulting polymer alloy fiber. However, if the A / B value is too large, the presence of island component fibers with significantly different diameters within the fiber may result in unstable elongation deformation behavior and excessive thickness unevenness in the fiber axis direction of the resulting polymer alloy fiber. Therefore, the A / B value is preferably less than 40.

[0034] The thickness unevenness in the fiber axis direction mentioned here is the Worcester (fineness unevenness) U It can be expressed as a value of %, and U% is preferably less than 1.0%. If U% is less than 1.0%, for example, when this fiber is processed into a textile, the degree of color variation and unevenness that appears will be more natural, and a high-quality textile can be obtained.

[0035] Furthermore, an A / B value of 5 or more has the effect of stabilizing spinnability and suppressing the occurrence of excessive thickness unevenness in the fiber axis direction of the obtained polymer alloy fiber, but to obtain a greater effect, an A / B value of 10 or more is more preferable.

[0036] In the cross section of the polymer alloy fiber of the present invention, the ratio (C / D) of the island component ratio (C) in the region within 30% from the fiber surface toward the fiber center to the island component ratio (D) in the entire fiber cross section is preferably 1.2 or more. Within this range, many island components are present near the fiber surface, and when the desired function is significantly affected by the properties of the fiber surface, the function can be efficiently exhibited even if the island component mixing ratio in the entire fiber is reduced.

[0037] If the C / D value is 1.2 or more, efficient function can be exhibited even with a small amount of island components. However, many unnecessary island components still exist in the inner fiber layer, which may cause a decrease in mechanical properties. Therefore, the C / D value is more preferably 1.5 or more.

[0038] The island component ratio in the present invention is calculated by the following formula: Island component ratio = (total area of ​​island components in the target area / total area of ​​the target area) × 100 (2) The total area of ​​island component parts in the target region and the total area of ​​the target region are calculated as follows. Specifically, a cross section of a single polymer alloy fiber perpendicular to the fiber axis is photographed using a transmission electron microscope (TEM) or a scanning electron microscope (SEM) at a magnification that allows observation of the entire cross section and all island component polymers. At this time, metal staining can be applied as needed to enhance the contrast between the sea component and the island component parts. From the two-dimensionally photographed image, the total area of ​​the target region and the area of ​​each island component part within the target region can be calculated using image processing software (e.g., WinROOF manufactured by Mitani Corporation). These values ​​are measured in nm units to one decimal place and rounded off. The target region here refers to the entire cross section of the fiber or a region within 30% of the fiber surface toward the fiber center.

[0039] The polymers constituting the polymer alloy fiber of the present invention may be selected from multiple polymers as appropriate depending on the application, but two types of polymers are preferred from the viewpoints of desired functional components, effectively expressing the functional components' functions, and controlling the stability of the cross-sectional morphology, etc. Specific combinations include polyester-based combinations such as high-viscosity polyethylene terephthalate / low-viscosity polyethylene terephthalate, polyethylene terephthalate / 5-sodium sulfoisophthalate (SSIA)-polyethylene glycol (PEG) copolymer polyethylene terephthalate, polybutylene terephthalate / polyethylene terephthalate, polytrimethylene terephthalate / polyethylene terephthalate, thermoplastic polyurethane / polyethylene terephthalate, polyester-based elastomer / polyethylene terephthalate, polyester-based elastomer / polybutylene terephthalate; polyamide-based combinations such as high-viscosity nylon 6 / low-viscosity nylon 6, nylon 6-nylon 66 copolymer / nylon 6 or 610, PEG copolymer nylon 6 / nylon 6 or 610, and thermoplastic polyurethane / nylon 6 or 610; and polyolefin-based combinations such as ethylene-propylene rubber finely dispersed polypropylene / polypropylene and propylene-α-olefin copolymer / polypropylene. Examples of combinations with low affinity include polyethylene terephthalate / nylon 6, polyethylene terephthalate / nylon 66, polyethylene terephthalate / polypropylene, polyethylene terephthalate / polyethylene, nylon 6 / polypropylene, nylon 6 / polyethylene, nylon 66 / polypropylene, nylon 66 / polyethylene, etc. The polymer may also contain various additives such as inorganic substances such as titanium oxide, silica, and barium oxide, colorants such as carbon black, dyes, and pigments, flame retardants, fluorescent brighteners, antioxidants, and ultraviolet absorbers.

[0040] To induce the unique phenomenon of island component fibers being unevenly distributed near the fiber surface, which is a feature of the present invention, it is preferable to use a combination of polymers in which the ratio of maximum viscosity to minimum viscosity is 1.5 times or more. As will be described in detail later, within this range, the low-viscosity polymers present as island components will efficiently move to the wall surface, and uneven distribution of island components will be induced without any problems. Although uneven distribution will be induced if the viscosity ratio is 1.5 times or more, it is more preferable that it is 5.0 times or more to make uneven distribution more pronounced and further widen the size distribution of the island components. The viscosity ratio referred to here is determined by measuring the viscosity of each polymer at a shear rate (1216 s) using a capillograph manufactured by Toyo Seiki Co., Ltd. -1 The measurement temperature should be set appropriately depending on the polymer and polymer combination used. For example, in the case of a polyester polymer combination, the measurement is performed at 290°C.

[0041] Furthermore, by combining polyester polymers with a maximum viscosity to minimum viscosity ratio of 1.5 or more as the polymers constituting the polymer alloy fiber of the present invention, a large amount of low-viscosity polyester is present near the fiber surface, suppressing high orientation and high crystallization, thereby obtaining a fiber with good abrasion resistance. Furthermore, when a high-viscosity polyester is used for the sea component, high strength is possible, and the polymer alloy fiber of the present invention can be used as a high-density thin fabric for sports and outdoor clothing, which can be used for a wide range of applications.

[0042] An example of the method for producing the polymer alloy fiber of the present invention will be described in detail below.

[0043] The polymer alloy fiber of the present invention can be produced by a known spinning method, for example, by kneading the polymer alloy in a melt kneading extruder such as an extruder, and the resulting mixture can be made into a polymer alloy fiber based on a melt spinning method. In this process, the melt-kneaded polymer alloy is subjected to a shear rate of 50 to 3000 s in a flow channel having a length 10 times or more relative to the flow channel diameter. ―1 It is necessary to make it flow.

[0044] In order to induce the unique phenomenon of the polymer alloy fiber of the present invention, in which the island components of the melt-mixed polymers are unevenly distributed near the fiber surface, it is important to control the pressure drop in the flow field. That is, when multiple polymers with different viscosities are mixed and flowed, a phenomenon is induced in which the gradient of the pressure drop in the flow channel is minimized to stabilize the flow field.

[0045] Therefore, if there is a difference in the fluidity of the mixed polymers, the component with good fluidity, for example, a low viscosity component, will be pushed out near the wall of the flow channel. In this case, as the pressure drop gradient in the flow channel becomes more pronounced, the phenomenon of the low viscosity component being pushed out near the wall becomes more pronounced, and in long flow channels, etc., the low viscosity component will be unevenly distributed in the polymer alloy.

[0046] This technological concept is based on the discovery of a unique phenomenon that occurs when a polymer alloy, which is a mixture of two or more polymers, flows in a special flow field, and the flow channel that creates this special flow field is important. The flow channel here refers to the path through which the molten polymer flows, and the special flow field can be controlled by adjusting the flow channel diameter and length.

[0047] The term "channel diameter" as used herein refers to the diameter of a cross section of a channel through which a polymer flows when the channel is viewed perpendicularly to the direction of polymer flow, and if the cross section is not circular, refers to the equivalent diameter calculated by converting the area determined from the cross section into a circle. The term "channel length" as used herein refers to the length of a line connecting the center of the cross section at the channel inlet to the center of the cross section at the channel outlet along the direction of polymer flow.

[0048] A flow path having a flow path length 10 times or more the flow path diameter used in the production of the polymer alloy fiber of the present invention means that the ratio of the flow path length to the flow path diameter is sufficiently long compared to flow paths used in conventional melt spinning processes.

[0049] This special flow path may be installed anywhere from when the mixed polymer is melted by a heater or the like, passes through each melt spinning member, and is then discharged in the form of fibers from the nozzle, and the specifications can be tailored to suit the melt spinning apparatus, piping, spinning pack, etc. However, when it is necessary to more significantly enhance the characteristic fiber cross section in which the target polymer is unevenly distributed, it is preferable to discharge the polymer flow in the form of fibers from the nozzle immediately after the uneven distribution phenomenon is induced by the special flow field, and it is preferable for the special flow path to be installed in any of the members of the melt spinning pack, including the spinneret.

[0050] In this case, when a combination of polymers with low affinity or a combination of polymers with significantly different melting points is produced at the same melting temperature, the effect of suppressing polymer degradation and excessive recombination of unevenly distributed components can be obtained. For this reason, this can be cited as a preferred embodiment for producing the polymer alloy fiber of the present invention. Furthermore, from the viewpoint of controlling a special composite flow in which one component is unevenly distributed, it is more preferable to provide a flow path for carrying out the present invention in the spinneret.

[0051] By drilling a flow path used to implement the present invention in a spinneret, the above-mentioned effects of the present invention can be effectively exerted on the collected fibers. In addition, it becomes possible to change various controlled fiber cross sections by relatively simple changes to components, etc., which is advantageous from an industrial point of view, as it does not require the securing of unnecessary components or the complicated modification of the spinning device.

[0052] In the production of the polymer alloy fiber of the present invention, it is necessary to flow the material under specific flow conditions in the special flow path described above, and by meeting these two requirements, it is possible to induce a unique phenomenon in which one component of the mixed polymer is unevenly distributed.

[0053] The specific flow conditions are based on the principle of using shear stress to move the mixed polymer components in the cross-sectional direction, and it is important to keep the shear rate in the flow within a specific range. In other words, the shear rate in the polymer flow in the channel is 50 to 3000 s-1 It is necessary to control it so that

[0054] The shear rate referred to here is uniquely determined based on the melt density of the polymer to be flowed, the discharge rate, and the diameter of the flow path according to the following formula, and can be controlled by setting the discharge rate to desired conditions. Shear rate = discharge amount / {π × melt density × (channel diameter) 2} (3) The discharge rate here refers to the mass of the measured molten polymer flowing through the flow path in one minute, and the melt density is a characteristic value according to the polymer composition used, so a known value can be used. For polymer compositions in which different polymers are mixed, it is possible to calculate the melt density by applying the melt density estimated from the blend ratio based on the melt density specific to the polymer, based on formula (3). For example, for polyethylene terephthalate (melt density 1.18 g / cm 3 ) and nylon 6 (melt density 0.74 g / cm 3 ) in a 70:30 blend of polymers, the value is 1.18 x 0.7 + 0.74 x 0.3 = 1.05 g / cm 3 The melt density of the mixed polymer is estimated, and the shear rate is calculated based on equation (3).

[0055] When implementing the present invention, it is important that the flow path specifications are designed three-dimensionally so that the flow path length relative to the flow path diameter satisfies the above-mentioned range, and the flow path form and cross-sectional shape should be installed to suit the equipment and components to be installed.

[0056] When using a simple long channel, in order to induce this unique phenomenon in the flow field, it is necessary to flow the polymer through a dedicated long channel at a low speed. In particular, in melt molding processes, resin degradation due to hydrolysis and oxidative decomposition can become an issue as the polymer flows through the channel. In polymers in which two or more different polymers are mixed in a molten state, the decomposition products of one polymer can accelerate the degradation of the other polymer. This can affect the processability of the fiber molding process and prevent the expected effects from being achieved in the final fiber properties, making it difficult to apply this to actual molding processes.

[0057] In particular, among melt molding processes, in processes such as melt spinning, in which the polymer flow rate is low and the residence time in the molten state is long, the above-mentioned effects are often noticeable, making application of such processes more difficult than in general melt molding processes. In response to these problems of the prior art, the present inventors have conducted extensive research and discovered a unique phenomenon in which one component of multiple melt-mixed polymers is unevenly distributed in a melt spinning process without unnecessarily complicating the equipment, and have succeeded in applying this phenomenon to processes such as melt spinning.

[0058] The flow channels required for the production method of the polymer alloy fiber of the present invention are designed in advance so that the channel length relative to the channel diameter satisfies the aforementioned range. However, the specifications of the flow channels installed in the component can be measured in the following manner. Specifically, indirect and nondestructive measurements are applicable to the evaluation of flow channel specifications for a variety of components. Among these, measurements using image analysis software to acquire continuous cross-sectional images using an X-ray CT scanner are particularly suitable for the present invention. Specifically, 3D CT images are taken using a Shimadzu XDimensus 300. These are then converted to grayscale images using image analysis software from Mitani Corporation's WinROOF. The threshold is adjusted and binarization is performed to extract the cross-section of the flow channel, and the area and perimeter are measured.

[0059] In the method for producing a polymer alloy fiber of the present invention, the flow path length should be set appropriately depending on the intended application within a range of 10 times or more the flow path diameter, but if the pressure loss is increased and the uneven distribution becomes more pronounced, the flow path length is preferably 30 times or more the flow path diameter. However, if the flow path is made too long, it may not be applicable to the spinning process or polymers with low heat resistance may not be able to be used due to the long residence time, so it is more preferable that the flow path length be 30 to 100 times the flow path diameter.

[0060] In the manufacturing method of the present invention, the shear rate in the flow path is set to 50 to 3000 s -1 It should be set appropriately so that it flows within the range of 3000s -1 In the high shear rate region around 50 to 1000 s, the aggregated unevenly distributed layer may be cut off, suppressing uneven distribution. -1 In order to reduce the shear rate, when the same polymer and spinning temperature are used, methods such as reducing the discharge rate or increasing the flow path diameter based on formula (3) can be mentioned. However, when the discharge rate is reduced, the residence time becomes longer, which may cause thermal degradation, so it is preferable to reduce the flow path diameter.

[0061] In the method for producing a polymer alloy fiber of the present invention, the polymer extrusion rate per nozzle can be in the range of 0.1 g / min / hole to 20.0 g / min / hole, which allows melt extrusion while maintaining stability. It is preferable to consider the pressure loss in the nozzle to ensure stable extrusion. The pressure loss here is preferably 0.1 MPa to 40 MPa, and the extrusion rate is preferably determined within this range based on the relationship between the melt viscosity of the polymer, the nozzle diameter, and the nozzle length.

[0062] When spinning the polymer alloy fiber of the present invention, the ratio of the high-viscosity component polymer to the low-viscosity component polymer can be selected from a weight ratio range of 5 / 95 to 95 / 5 based on the discharge rate. Within this range, uneven distribution is induced and stable production is possible, but depending on the viscosity difference between the polymers, if the sea component is a high-viscosity component, the low-viscosity component may be difficult to extrude to the outside, so the polymer ratio is preferably 5 / 95 to 70 / 30.

[0063] The polymer stream extruded from the nozzle is cooled and solidified, converged by adding an oil or the like, and taken up by rollers with a specified peripheral speed. In the present invention, from the viewpoint of stable production, the take-up speed of the rollers is preferably about 500 to 6000 m / min, but this can be changed depending on the physical properties of the polymer and the intended use of the fiber. During drawing, it is preferable to appropriately set the preheating temperature using the softening temperature, such as the glass transition temperature of the polymer, as a guide.

[0064] The upper limit of the preheating temperature is preferably set to a temperature at which spontaneous elongation of the fiber does not cause yarn path disturbance during the preheating process. For example, in the case of PET, which has a glass transition temperature of around 70°C, the preheating temperature is usually set to about 80 to 95°C. In addition, in the case of polymers that do not exhibit a glass transition, the dynamic viscoelasticity (tan δ) of the composite fiber is measured, and the preheating temperature can be set to a temperature equal to or higher than the peak temperature on the high-temperature side of the obtained tan δ.

[0065] From the viewpoint of increasing the draw ratio and improving the mechanical properties, it is also suitable to carry out this drawing in multiple stages. Regarding drawing, the spun conjugated fiber may be drawn after being temporarily wound up, or the drawing may be carried out immediately after spinning without being temporarily wound up. Furthermore, false twisting may be carried out in addition to drawing.

[0066] The false twisting method is not particularly limited as long as it is a method commonly used for polyesters and the like, but in consideration of productivity, it is preferable to use a friction false twisting machine using a disk or belt.

[0067] As described above, the method for producing the polymer alloy fiber of the present invention has been described. However, it goes without saying that the polymer alloy fiber can also be produced by the melt-blowing method and the spunbonding method, and further, it can also be produced by solution spinning methods such as wet and dry-wet methods. [Example]

[0068] The ultrafine fibers of the present invention will be specifically described below with reference to examples.

[0069] The examples and comparative examples were evaluated as follows.

[0070] A. Island diameter CV% and uneven distribution evaluation The average island component diameter and standard deviation of the cross section of the fiber in each example and comparative example were measured by the above-mentioned method (using SEM and image processing software WinROOF manufactured by Mitani Corporation), and the island component diameter CV% in the region within 30% from the fiber surface toward the fiber center was calculated using formula (1). The uneven distribution was evaluated based on each island component diameter CV% value using the following three levels. Very good S: 75% or more Good A: 50% or more, less than 75% Poor B: Less than 50%.

[0071] B. Ratio of average island component diameter (A / B) The average diameter of the island component fibers in the cross section of each example and comparative example was measured by the method described above (using SEM and image processing software WinROOF manufactured by Mitani Corporation), and the ratio (A / B) of the average island component diameter (A) within 30% from the fiber surface toward the fiber center to the average island component diameter (B) within 30% from the fiber center toward the fiber surface was calculated.

[0072] C. Worcester U% Using a Zellweger UT-4 fineness unevenness measuring device, the yarn speed was 100 m / min. The Worcester U% (H) of the polymer alloy fiber is measured under conditions of a twister rotation speed of 6000 rpm and a measurement length of 100 m. If the U% value is less than 1.0%, it is considered good (A), and if it is 1.0% or more, it is considered poor (B).

[0073] D. Island component ratio (C / D) For each fiber cross section of each Example and Comparative Example, the total area of ​​the target region and the area of ​​each island component within the target region were measured using the method described above (using SEM and image processing software WinROOF manufactured by Mitani Shoji), and the ratio (C / D) of the island component ratio (C) within 30% from the fiber surface toward the fiber center to the island component ratio (D) of the entire fiber cross section was calculated. Note that C and D were calculated using formula (2).

[0074] E. Polymer melt viscosity and viscosity ratio The chip-shaped polymer was dried in a vacuum dryer to a moisture content of 200 ppm or less, and the melt viscosity was measured using a Capillograph 1B manufactured by Toyo Seiki Seisaku-sho. Furthermore, the melt viscosity of the high-viscosity component polymer was divided by the melt viscosity of the low-viscosity component polymer, and the value was rounded to two decimal places to obtain the viscosity ratio. The measurement temperature was the same as the spinning temperature, and in the examples and comparative examples, a shear rate of 1216 s -1 The melt viscosity is shown in Table 1. The measurement was carried out in a nitrogen atmosphere, with a time interval of 5 minutes from when the sample was placed in the heating furnace to when the measurement started.

[0075] F. Abrasion resistance After preparing a cylindrical knitted fabric using a cylindrical knitting machine with a stitch count of 50, abrasion resistance was evaluated in accordance with JIS L1096 (2010) and Method E (Martindale method). The test was conducted using a standard polyester friction cloth with a pressure load of 9 kPa. The evaluation was based on the number of abrasions required until fuzzing occurred, and was rated on the following three-point scale. Very good S: 5000 times or more Good A: 3000 to less than 5000 times Defective B: Less than 3000 times.

[0076] G. Ratio of channel length to channel diameter Three-dimensional CT images were taken using a Shimadzu XDimensus300 and converted to grayscale images using Mitani Corporation's WinROOF image analysis software. After adjusting the threshold and performing binarization, the channel diameter was calculated by extracting the channel cross section and measuring its area and perimeter. The channel length was calculated by measuring the length of the line connecting the center of the cross section at the channel inlet to the center of the cross section at the channel outlet along the polymer flow direction. Furthermore, the value obtained by dividing the channel length by the channel diameter was rounded to two decimal places to obtain the ratio of channel length to channel diameter.

[0077] H. Shear rate The shear rate (s -1 ) was calculated using equation (3). The melt density was calculated using the value of polyethylene terephthalate (1.18 g / cm 3 ) to use.

[0078] I. Fineness The weight of 100 m of polymer alloy fiber was measured and the fineness was calculated by multiplying it by 100. This was repeated 10 times, and the simple average value was rounded to one decimal place to obtain the fineness.

[0079] [Example 1] Two polymers were prepared to achieve a viscosity ratio of 1.5: polyethylene terephthalate (PET, melt viscosity: 120 Pa s) as the high-viscosity component polymer, and polyethylene terephthalate copolymerized with 8.0 mol% 5-sodium sulfoisophthalic acid and 9 wt% polyethylene glycol (SSIA-PEG copolymerized PET, melt viscosity: 80 Pa s) as the low-viscosity component polymer. The high-viscosity component polymer and the low-viscosity component polymer were adjusted to a weight ratio of 70 / 30 and melt-mixed at 290 °C using an extruder. The spinning temperature was then increased to 290 °C and the fibers were metered using a pump. The fibers were then spun at a shear rate of 50 s -1 The mixture was made to flow at 0.70 g / min / hole and discharged from the discharge holes.

[0080] The polymer stream discharged from the nozzle was cooled and solidified, then coated with an oil, wound up at a spinning speed of 1000 m / min, and stretched 3.0 times between rollers heated to 90°C and 130°C. Through the spinning and stretching process, a polymer alloy fiber of 56 dtex-24 filaments (single fiber fineness 2.3 dtex) was obtained.

[0081] The cross section of the obtained polymer alloy fiber was a cross section in which the high-viscosity component polymer was the sea component and the low-viscosity component polymer was the island component. The island component diameter CV% in the region within 30% from the fiber surface toward the fiber center was 76.1%, indicating that large island components were present locally in the fiber cross section and that uneven distribution was induced very well. Furthermore, the A / B value was 13.9, and despite the uneven distribution, U%, an index of fineness unevenness, was 0.7%, indicating excellent thickness uniformity in the fiber axis direction.

[0082] The cylindrical knitted fabric made of the polymer alloy fiber did not produce any fluff even after 5,000 abrasion cycles, demonstrating extremely good abrasion resistance. The results are shown in Table 1.

[0083] [Examples 2 and 3] The flow channel design allows the shear rate to reach 500 s -1 (Example 2), 1000s -1 In Example 3, a polymer alloy fiber of 56 dtex and 24 filaments was obtained in the same manner as in Example 1 except that the flow was carried out.

[0084] By increasing the shear rate in the flow channel compared to Example 1, the pressure loss in the flow channel increased and the island components were more likely to aggregate, so that the island component diameter CV% in the region within 30% from the fiber surface toward the fiber center in the cross section of the obtained polymer alloy fiber was 83.1% (Example 2) and 88.3% (Example 3), which showed better induced uneven distribution of the island components than Example 1. In addition, the A / B value was 22.1 (Example 2) and 27.4 (Example 3), and although uneven distribution was induced, U%, an index of fineness unevenness, was 0.8%, and the thickness uniformity in the fiber axis direction was excellent.

[0085] The tubular knitted fabric made of the polymer alloy fiber showed no fuzzing even after 6,000 abrasion cycles, demonstrating excellent abrasion resistance. The results are shown in Table 1.

[0086] [Example 4] The flow channel design allows the shear rate to reach 3000 s -1 A polymer alloy fiber of 56 dtex and 24 filaments was obtained in the same manner as in Example 1 except that the flow rate was 100 rpm.

[0087] Although the pressure loss in the flow channel increased by increasing the shear rate in the flow channel compared to Example 1, the island component fibers were cut by the high shear, and the island component diameter CV% in the region within 30% from the fiber surface toward the fiber center in the cross section of the obtained polymer alloy fiber was 64.2%, confirming uneven distribution of the island component fibers. Furthermore, the A / B value was 8.3, and despite the uneven distribution, U%, an index of fineness unevenness, was 0.6%, indicating excellent thickness uniformity in the fiber axis direction.

[0088] The cylindrical knitted fabric made of the polymer alloy fiber showed no fuzzing even after 4,500 abrasion cycles, demonstrating good abrasion resistance. The results are shown in Table 1.

[0089] [Example 5] A polymer alloy fiber of 56 dtex-24 filaments was obtained in the same manner as in Example 1, except that the polymer was caused to flow in a long flow path whose length was 10 times the flow path diameter.

[0090] Since the flow paths were shorter than those in Example 1, the pressure loss in the flow paths was lower, and the island component diameter CV% in the region within 30% from the fiber surface toward the fiber center in the cross section of the obtained polymer alloy fiber was 52.8%. The A / B value was 5.3, and although uneven distribution was induced, U%, an index of fineness unevenness, was 0.6%, indicating excellent thickness uniformity in the fiber axis direction.

[0091] The cylindrical knitted fabric made of the polymer alloy fiber showed no fuzzing even after 4,500 abrasion cycles, demonstrating good abrasion resistance. The results are shown in Table 1.

[0092] [Examples 6 and 7] A polymer alloy fiber of 56 dtex-24 filaments was obtained in the same manner as in Example 1, except that the polymer was flowed in a long channel whose length was 70 times (Example 6) or 100 times (Example 7) the channel diameter.

[0093] By using longer flow channels than in Example 1, the pressure loss in the flow channels increased and the island components were more likely to aggregate, so the island component diameter CV% in the region within 30% from the fiber surface toward the fiber center in the cross section of the obtained polymer alloy fiber was 84.5% (Example 6) and 95.3% (Example 7), which showed extremely favorable induced uneven distribution of the island components compared to Example 1. Furthermore, the A / B values ​​were 25.8 (Example 6) and 32.7 (Example 7), and although uneven distribution was induced, U%, which is an index of fineness unevenness, was 0.7% (Example 6) and 0.9% (Example 7), showing excellent thickness uniformity in the fiber axis direction.

[0094] The tubular knitted fabric made of the polymer alloy fiber showed no fuzzing even after 6,000 abrasion cycles, demonstrating excellent abrasion resistance. The results are shown in Table 1.

[0095] [Example 8] A polymer alloy fiber of 56 dtex and 24 filaments was obtained in the same manner as in Example 1, except that high-molecular-weight polyethylene terephthalate (high-molecular-weight PET, melt viscosity: 650 Pa s) was used as the high-viscosity component polymer and PET (melt viscosity: 120 Pa s) was used as the low-viscosity component polymer, so that the viscosity ratio was 5.4.

[0096] The island component diameter CV% in the region within 30% from the fiber surface toward the fiber center in the cross section of the obtained polymer alloy fiber was 52.0% because the pressure loss in the flow channel increased and the island component particles were more likely to aggregate by increasing the viscosity ratio compared to Example 1. The A / B value was 5.3, and although uneven distribution was induced, U%, an index of fineness unevenness, was 0.7%, indicating excellent thickness uniformity in the fiber axis direction.

[0097] The tubular knitted fabric made of the polymer alloy fiber showed no fuzzing even after 6,000 abrasion cycles, demonstrating excellent abrasion resistance. The results are shown in Table 1.

[0098] [Example 9] A polymer alloy fiber of 56 dtex-24 filaments was obtained in accordance with Example 1, except that high molecular weight PET was prepared as the high-viscosity component polymer and SSIA-PEG copolymerized PET was prepared as the low-viscosity component polymer so that the viscosity ratio was 8.1.

[0099] By increasing the viscosity ratio compared to Example 1 and Example 8, the pressure loss in the flow channel increased and the island components were more likely to aggregate, so that the island component diameter CV% in the region within 30% from the fiber surface toward the fiber center in the cross section of the obtained polymer alloy fiber was 97.4%, and the uneven distribution was better compared to Example 1 and Example 8. In addition, the A / B value was 5.3, and although uneven distribution was induced, U%, which is an index of fineness unevenness, was 0.9%, and the thickness uniformity in the fiber axis direction was excellent.

[0100] The cylindrical knitted fabric made of the polymer alloy fiber showed no fuzzing even after 7,000 abrasion cycles, demonstrating extremely good abrasion resistance. The results are shown in Table 1.

[0101] [Table 1]

[0102] [Comparative Example 1] The flow path design allows for a shear rate of 25 s -1 A polymer alloy fiber of 56 dtex and 24 filaments was obtained in the same manner as in Example 1 except that the flow rate was 100 rpm.

[0103] By lowering the shear rate in the flow channel compared to Example 1, the pressure loss in the flow channel was reduced, and the island components were finely dispersed relatively uniformly. The island component diameter CV% in the region within 30% from the fiber surface toward the fiber center in the cross section of the obtained polymer alloy fiber was 25.1%, which is a cross-sectional morphology that is difficult to say induces the uneven distribution of island components, which is a feature of the present invention.

[0104] The cylindrical knitted fabric made of the polymer alloy fiber generated fluff after 2000 abrasion cycles, and was found to have poor abrasion resistance. The results are shown in Table 2.

[0105] Comparative Example 2 The flow path design allows the shear rate to reach 4000 s -1 A polymer alloy fiber of 56 dtex and 24 filaments was obtained in the same manner as in Example 1 except that the flow rate was 100 rpm.

[0106] Since the shear rate in the flow channel was too high compared to Example 1, the pressure loss in the flow channel increased, while the island components were cut by the high shear. As a result, the island component diameter CV% in the region within 30% from the fiber surface toward the fiber center in the cross section of the obtained polymer alloy fiber was 30.2%, and the island components were relatively uniformly finely dispersed in the fiber cross section.

[0107] The cylindrical knitted fabric made of the polymer alloy fiber generated fluff after 2,500 abrasion cycles, and was found to have poor abrasion resistance. The results are shown in Table 2.

[0108] Comparative Example 3 A polymer alloy fiber of 56 dtex-24 filaments was obtained in the same manner as in Example 1, except that the polymer was caused to flow in a long flow channel whose length was five times the flow channel diameter.

[0109] By using a flow path shorter than that in Example 1, the pressure loss in the flow path was reduced and the island components were uniformly and finely dispersed. Therefore, the island component diameter CV% in the region within 30% from the fiber surface toward the fiber center in the cross section of the obtained polymer alloy fiber was 27.4%, and the island components, which are a feature of the present invention, were not induced very much.

[0110] The cylindrical knitted fabric made of the polymer alloy fiber generated fluff after 2,500 abrasion cycles, and was found to have poor abrasion resistance. The results are shown in Table 2.

[0111] Comparative Example 4 A polymer alloy fiber of 56 dtex-24 filaments was obtained in accordance with the same procedures as in Example 1, except that a long flow path with a flow path length 9 times the flow path diameter was used, and PET (melt viscosity: 120 Pa s) was used as the high-viscosity component polymer and polyethylene terephthalate copolymerized with 7 mol% isophthalic acid (IPA-copolymerized PET, melt viscosity: 100 Pa s) was used as the low-viscosity component polymer so that the viscosity ratio was 1.2.

[0112] By lowering the viscosity ratio compared to Example 1, the pressure loss in the flow channel was reduced and the island parts were uniformly and finely dispersed. Therefore, the island part diameter CV% in the region within 30% from the fiber surface toward the fiber center in the cross section of the obtained polymer alloy fiber was 26.5%, and the island parts, which are a feature of the present invention, were not induced very much. The cylindrical knitted fabric made of the polymer alloy fiber generated fluff after 2,500 abrasion cycles, and was found to have poor abrasion resistance. The results are shown in Table 2.

[0113] [Table 2] [Explanation of symbols]

[0114] A: Region where island components are evenly dispersed B: Region where uneven distribution of island components is induced C: Fiber surface D: Fiber center E: Area within 30% from the fiber surface toward the fiber center F: Area within 30% from the fiber center toward the fiber surface 1:Measuring plate 2:Measuring hole 3: Long flow path plate 4: Long channel 5:Discharge plate 6:Discharge hole 7: Flow path length 8: Flow channel cross section 9: Channel diameter

Claims

1. A polymer alloy fiber characterized in that, in a fiber cross section in which a plurality of polymers are separated into a sea part and island parts, the island part diameter CV% is 50% or more in a region within 30% from the fiber surface toward the fiber center, and each island part exists discontinuously in the fiber axis direction.

2. A polymer alloy fiber characterized in that, in a fiber cross section in which a plurality of polymers are separated into a sea part and island parts, the ratio (A / B) of the average diameter of the island parts within 30% from the fiber surface toward the fiber center to the average diameter of the island parts within 30% from the fiber center toward the fiber surface is 5 or more, and each island part is present discontinuously in the fiber axis direction.

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