Polymer alloy fiber manufacturing method

Abstract

To provide a method for producing polymer alloy fibers that allows functional components and functional particles to function efficiently by flowing at a high shear rate in a long channel to unevenly distribute island components scattered in a sea component of the polymer alloy fibers.SOLUTION: A method for producing a synthetic fiber comprises spinning after allowing polymers to flow at a shear rate of 50 to 3000 s-1 in a channel where a channel length relative to a channel diameter is 10 times or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing 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 been widely used in a wide range of applications, from clothing to industrial uses such as interiors and vehicle interiors, due to their excellent mechanical properties and dimensional stability. As the required properties for these applications have diversified, various functional fibers have been developed. For example, by reducing the fiber diameter, a soft texture can be imparted, and by changing the fiber cross section from a standard round cross section to a modified cross section, moisture absorption and quick-drying properties or a different appearance can be imparted. Furthermore, the polymers that make up the fibers themselves may contain functional particles or be copolymerized with other components to impart new functionality such as transparency prevention or UV protection, or two or more polymers may be used to create composite fibers.

[0003] Such composite fibers can combine functions that cannot be achieved with a single polymer, and can even be endowed with completely new functions, and have become a mainstream technology in the production of functional fibers.

[0004] 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.

[0005] There are various methods for the polymer alloy method, such as dry blending two or more resins and melting them in a mixed state, or kneading the combined resins in advance using a melt extruder 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.

[0006] In the polymer alloy fiber, by utilizing a compatibilizer or the like, which is an intermediate component of the combined polymers, island component fibers are uniformly finely dispersed in the sea component, thereby making it possible to overcome defects of the sea component polymer and improve its functionality, and this technology is disclosed in Patent Document 1 or Patent Document 2.

[0007] 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. Patent Document 1 claims that by combining the properties of each polymer, it is possible to produce a polymer alloy fiber that combines heat resistance and dyeability, something that has not been achieved before.

[0008] Furthermore, in Patent Document 2, polyolefin copolymerized with an acid anhydride group-containing unsaturated compound is melt-mixed with polyamide, and the polyolefin is finely dispersed in the polyamide matrix, thereby suppressing the dimensional change caused by water absorption and moisture absorption, which has been a problem with polyamide fibers, and as an additional effect, it is said to be possible to produce polymer alloy fibers with vivid dyeability and a unique texture. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2010-15072 A (Claims) [Patent Document 2] JP 7-70822 A (Claims) Summary of the Invention [Problem to be solved by the invention]

[0010] Patent Document 1 aims to improve heat resistance by finely dispersing highly heat-resistant polylactic acid in polypropylene, which is a sea component. However, when the bulk properties of the polymer alloy fiber are evaluated, the heat resistance is certainly improved, but since there are portions in the outermost fiber layer where polypropylene, which has low heat resistance, is exposed, when the fiber is heated and a compressive force is applied, for example, when heated with an iron, or when the fiber is heated as a bundle, the polypropylene in the surface layer of the fiber melts, causing the fiber to collapse or causing fusion between adjacent fibers, and it is difficult to say that practical heat resistance has been imparted.

[0011] In Patent Document 2, a sea component is made of polyamide and an island component is made of polyolefin, and a highly hydrophobic polyolefin is dispersed and mixed with a highly water-absorbent and hygroscopic polyamide, thereby expecting to suppress dimensional change due to swelling due to water absorption, which is a problem with fibers made solely of polyamide. However, in Patent Document 2, as in Patent Document 1, the outermost layer of the fiber that substantially comes into contact with water has a portion where polyamide exists alone, and moisture is absorbed from there, so that the expected degree of dimensional change suppression effect may not be obtained.

[0012] 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 the fibers functions such as heat resistance and hydrophobicity that cannot be achieved with the sea component polymer alone.

[0013] However, in Patent Documents 1 and 2, the island component particles are basically uniformly dispersed, and their arrangement in the fiber cross section cannot be arbitrarily determined. This may prevent effective utilization of the island component particles' 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 the target properties depend on changes in the properties of the outermost layer of the fiber, it becomes necessary to increase the island component content in the outermost layer, which naturally leads to an excessive increase in the island component content. In this case, although the functional polymer is indeed arranged in the surface layer of the fiber, the excess island component particles arranged in the inner layer do not exert their effects, and in the fiber as a whole, many unnecessary island component particles are present. In this case, the presence of many unnecessary island component particles in the inner layer may result in a deterioration in the mechanical properties, which are the basic properties of the fiber, or the properties of the sea component polymer that were originally required may not be fully exhibited, thereby failing to achieve the intended effect of adopting the polymer alloy method.

[0014] Furthermore, when the mixing ratio of island components needs to be increased more than necessary, it is necessary to control the mixing conditions in a complicated manner in order to suppress the fluctuation of the mixing ratio over time. Also, a polymer alloy in which the ratio of two types of polymers is present without bias often has a complicated rheological property in which the fluidity of the two types of polymers exists, which results in an unstable discharge behavior when discharged from a spinneret, and sometimes significantly reduces spinnability.

[0015] Therefore, there has been a demand for a manufacturing method capable of controlling the dispersion state of island component fibers in a polymer alloy fiber, and a demand for a manufacturing method for a polymer alloy fiber capable of controlling the dispersion form of island component fibers and further the arrangement thereof. [Means for solving the problem]

[0016] The object of the present invention is achieved by the following means: (1) In a channel where the channel length is 10 times or more the channel diameter, The ratio of maximum viscosity to minimum viscosity is 1.5 times or more Multiple polymers Mixed polymers of Shear rate: 50 to 3000 s-1 and then spinning the resulting polymer alloy fiber. (2) The method for producing a polymer alloy fiber according to claim 1, characterized in that the length of the flow path is 30 times or more the diameter of the flow path. (3) The shear rate of multiple polymers in the channel is 50 to 1000 s -1 3. The method for producing a polymer alloy fiber according to claim 1, wherein the polymer alloy fiber is is. [Effects of the Invention]

[0017] The production method of the present invention can provide a method for producing a polymer alloy fiber in which a plurality of polymers are melt-mixed, in which island component fibers scattered in a sea component are unevenly distributed, thereby allowing functional components or functional particles to function efficiently. [Brief explanation of the drawings]

[0018] [Figure 1] 1A and 1B are diagrams showing a long flow path used in the present invention, in which (a) is a schematic diagram of a spinneret in which a long flow path is installed, (b) is a schematic diagram of a long flow path installed in the spinneret, and (c) is a schematic diagram of a cross section of the long flow path. [Figure 2] 1 is a schematic diagram of a cross-sectional structure of a polymer alloy fiber produced according to the present invention, in which island components are induced to be unevenly distributed. DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention will be described in detail below together with preferred embodiments.

[0020] In the melt spinning process of the present invention, a plurality of polymers are spun at a shear rate of 50 to 3000 s in a channel having a length 10 times or more relative to the diameter of the channel. -1 It is necessary to make it flow.

[0021] To induce the unique phenomenon of island component distribution near the fiber surface of melt-mixed polymers, which is a feature of the present invention, 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 of minimizing the pressure drop gradient in the flow channel is induced to stabilize the flow field. Therefore, if the mixed polymers have different melt viscosities or fluidities, the component with good fluidity, for example, low viscosity, is extruded 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 low viscosity component being extruded near the wall becomes more pronounced, and in long flow channels, etc., the low viscosity component is extruded more strongly. This induces the uneven distribution of the low viscosity component in the polymer alloy.

[0022] The technical concept of this invention 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 path that creates this special flow field is important. The flow path here refers to the path through which the molten polymer flows, and the special flow field can be controlled by the flow path diameter and length.

[0023] In the present invention, the channel diameter 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. In addition, the channel length 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.

[0024] To achieve the special flow field required for the achievement of the present invention, the length of the flow channel must be 10 times or more the diameter of the flow channel, which is the first requirement of the present invention.

[0025] A flow path used in the present invention, in which the flow path length is 10 times or more the flow path diameter, means that the ratio of the flow path length to the flow path diameter is sufficiently long compared to a flow path used in a normal melt spinning process. To achieve the present invention, this special flow path only needs to be installed somewhere along the path from when the mixed polymers are melted by a heater or the like, passed through each melt spinning element, and then discharged in the form of fibers from the nozzle of the spinneret, and it can be tailored to suit the melt spinning apparatus, piping, spin pack, etc. used. However, when it is necessary to more significantly enhance the characteristic fiber cross section in which one of the polymers is unevenly distributed, which is the objective of the present invention, 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 a special flow field, and it is preferable for the special flow path to be installed in any of the components of the melt spinning pack, including the spinneret.

[0026] In this case, when a combination of polymers with low affinity or 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 achieved. Therefore, this can be cited as a preferred embodiment 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 spinneret with a flow path for implementing the present invention. By providing a spinneret with a flow path used to implement the present invention, the above-mentioned effects of the present invention can be effectively exerted on the collected fibers. Furthermore, it becomes possible to change various controlled fiber cross sections by relatively simple changes to components, etc., which is advantageous from an industrial viewpoint, for example, by eliminating the need for unnecessary components or complex modifications to the spinning apparatus.

[0027] In the present invention, it is necessary to flow 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.

[0028] 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 This is the second requirement of the present invention.

[0029] The shear rate referred to in the present invention 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, but in the present invention, it can be controlled by setting the discharge rate to desired conditions. Shear rate = discharge amount / {π × melt density × (channel diameter) 2} (1) 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, and a known value can be used. In the case of a polymer composition 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 (1). For example, 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 = 1.42 g / cm 3 The melt density of the mixed polymer is estimated, and the shear rate is calculated based on equation (1).

[0030] 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.

[0031] When using a simple long channel, in order to induce this unique phenomenon in the flow field, the polymer needs to flow at a low speed through a dedicated long channel. 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 the case of 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 or prevent the expected effects from being achieved in the final fiber properties, making it difficult to apply this to actual molding processes.

[0032] In particular, among melt molding processes, the above-mentioned effects are often more pronounced in processes such as melt spinning, in which the polymer flow rate is low and the residence time in the molten state is long, 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.

[0033] The specifications of the flow channels required for implementing this invention are determined in advance during component design so that the flow channel length relative to the flow channel diameter satisfies the aforementioned range. However, the specifications of the flow channels installed in the component can be measured using the following method. Specifically, indirect and nondestructive measurements are applicable to a variety of components when evaluating flow channel specifications. Among these, measurements using image analysis software to acquire continuous cross-sectional images using an X-ray CT scanner are particularly suitable for this invention. Specifically, 3D CT images are taken using a Shimadzu XDimensus300. These are then converted to grayscale images using Mitani Corporation's WinROOF image analysis software. The cross-section of the flow channel is extracted by adjusting the threshold and binarizing the image, and the area and perimeter are measured.

[0034] In the production method of the present invention, the channel length should be set appropriately depending on the intended application within a range of 10 times or more the channel diameter. However, if the pressure loss is increased and the uneven distribution becomes more pronounced, the channel length is preferably set to 30 times or more the channel diameter. However, if the channel is made very long, it may not be applicable to the spinning process or may result in an unnecessarily long residence time, making it impossible to use polymers with low heat resistance. Therefore, it is more preferable that the channel length is set to 30 times or more and 100 times or less the channel diameter. Furthermore, in the production method of the present invention, the shear rate in the channel 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 from equation (1) or increasing the flow path diameter 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.

[0035] The term "polymer alloy" as used herein refers to a blend of multiple polymers separated into a sea component and island components. For example, the polymer alloy can be obtained by kneading in a melt kneading extruder such as an extruder, and polymer alloy fibers can be obtained by a known spinning method, for example, melt spinning. The term "island component" as used herein refers to the island component of different components separated into an island-in-sea structure by blending. The term "island-in-sea structure" also refers to the island component being separated into multiple parts by the sea.

[0036] The polymer alloy fiber produced by the present invention must be flowed under specific flow conditions in the special flow path described above. Meeting these requirements enables the induction of a unique phenomenon in which one component of the mixed polymer is unevenly distributed. The term "uneven distribution" as used herein refers to a case in which the island component diameter CV% scattered within the fiber cross section is 20% or more. The island component diameter CV% is determined by the method described below. A large value indicates that there is a distribution in the island component sizes present within the same fiber cross section, with large island components being present locally. For typical polymer alloy fibers, this value is less than 20%, but when the uneven distribution of island components, which is the desired effect of the present invention, is induced, a distribution in the island component sizes occurs. An island component CV% of 20% or more is a measure of whether the effect of the present invention is being exerted. An island component diameter CV% of 20% or more indicates that uneven distribution is induced, and falls within the preferred range of the present invention. Pursuing this idea, it is preferable that the size distribution of the island component fibers is large, and from the viewpoint of more effectively exhibiting the desired function, it is more preferable that the island component diameter CV% is 30% or more.

[0037] 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 (2) The standard deviation of diameter and average diameter referred to here are determined as follows. Specifically, a cross section perpendicular to the fiber axis of a single yarn of a polymer alloy fiber is photographed 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 applied, if necessary, to enhance the contrast between the sea component and the island component. From the two-dimensionally photographed image, the diameters of island component polymers randomly sampled within the same image are measured using image processing software (e.g., WinROOF manufactured by Mitani Corporation). Here, the island component polymers appearing in the fiber cross section are not necessarily perfectly circular. 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 diameter of each island component and calculating the simple number average, while the standard deviation of diameter is calculated from the diameter of each island component and the average diameter.

[0038] The multiple polymers used in the production method of the present invention are appropriately selected from two or more types of polymers depending on the application, but two types of polymers are preferred from the viewpoints of effectively expressing the desired functional components or functional components and controlling the stability of the cross-sectional morphology, etc. Specific combinations include polyester-based combinations such as polybutylene terephthalate / polyethylene terephthalate, polytrimethylene terephthalate / polyethylene terephthalate, thermoplastic polyurethane / polyethylene terephthalate, polyester-based elastomer / polyethylene terephthalate, and polyester-based elastomer / polybutylene terephthalate; polyamide-based combinations such as nylon 6-nylon 66 copolymer / nylon 6 or 610, polyethylene glycol (PEG) copolymerized 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.

[0039] In order to make the gradient of pressure drop in the flow channel more pronounced, it is preferable to combine these two types of polymers so that the ratio of the maximum viscosity to the minimum viscosity in the mixed polymer is 1.5 times or more. In this range, the low viscosity component efficiently moves to the wall surface, and the uneven distribution of island components, which is the objective of the present invention, is induced without any problems. Although uneven distribution is induced when the viscosity ratio is 1.5 times or more, it is more preferable that it is 5.0 times or more to make the uneven distribution more pronounced and further widen the size distribution of the island components. The viscosity ratio here is determined by measuring the viscosity of each polymer at the same temperature and shear rate (1216 s) using a capillograph manufactured by Toyo Seiki Seisaku-sho, etc. -1 ) and the melt viscosity ratio was calculated.

[0040] In the production method of the present invention, the polymer extrusion rate per nozzle can be set to 0.1 g / min / hole to 20.0 g / min / hole, which is the range that allows melt extrusion while maintaining stability. In this case, it is preferable to consider the pressure loss in the nozzle to ensure stable extrusion. The pressure loss referred to here is preferably set to 0.1 MPa to 40 MPa, and the extrusion rate is determined within this range based on the relationship between the melt viscosity of the polymer, the nozzle diameter, and the nozzle length.

[0041] The ratio of the high-viscosity component polymer to the low-viscosity component polymer when spinning the composite fiber used in the production method of the present invention can be selected within a weight ratio range of 5 / 95 to 95 / 5 based on the discharge amount. 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.

[0042] The molten polymer stream extruded from the nozzle is cooled and solidified, converged by the addition of an oil or other agent, and taken up by rollers with a specified peripheral speed. In the present invention, from the viewpoint of stable production, the roller take-up speed is preferably approximately 500 to 6,000 m / min, although 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 based on the softening temperature, such as the glass transition temperature of the polymer. 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, whose glass transition temperature is around 70°C, the preheating temperature is usually set to approximately 80 to 95°C. Furthermore, 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 selected to be equal to or higher than the peak temperature on the higher side of the obtained tan δ. Here, from the viewpoint of increasing the draw ratio and improving the mechanical properties, it is also preferable to perform this drawing process in multiple stages. Regarding drawing, the spun conjugate fiber may be drawn after being wound up, or may be drawn immediately after spinning without being wound up. False twisting may also be carried out in addition to drawing.

[0043] 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.

[0044] 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]

[0045] The ultrafine fibers of the present invention will be specifically described below with reference to examples.

[0046] The examples and comparative examples were evaluated as follows.

[0047] A. 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.

[0048] B. Shear rate The shear rate (s -1 ) was calculated using equation (1).

[0049] C. 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.

[0050] D. 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.

[0051] E. Uneven Distribution Assessment For each fiber cross section of each example and comparative example, the island component diameter CV% value was calculated using formula (2) and the uneven distribution was evaluated on the following three levels. Very good S: 40% or more Good A: 20% or more Defective B: Less than 20%.

[0052] [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.

[0053] 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.

[0054] The cross section of the obtained polymer alloy fiber was a cross section in which the high-viscosity component was the sea component and the low-viscosity component was the island component, and the island component diameter CV% value was 42.4%, indicating that large island components were present locally in the fiber cross section, and the uneven distribution of island components, which is the effect of the present invention, was extremely well induced. The results are shown in Table 1.

[0055] [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.

[0056] 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 the island component diameter CV% of the obtained polymer alloy fibers was 55.2% (Example 2) and 72.8% (Example 3), and the uneven distribution of the island components was better induced than in Example 1. The results are shown in Table 1.

[0057] [Example 4] The flow path 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.

[0058] By increasing the shear rate in the flow channel compared to Example 1, the pressure loss in the flow channel increased. However, the island component fibers were cut by the high shear, and the island component diameter CV% of the obtained polymer alloy fiber was 34.5%, confirming uneven distribution of the island components.

[0059] The results are shown in Table 1.

[0060] [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.

[0061] The pressure loss in the flow channels was lower because the flow channels were shorter than in Example 1, and the obtained polymer alloy fiber had an island component diameter CV% of 25.4%. The results are shown in Table 1.

[0062] [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.

[0063] 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% of the obtained polymer alloy fibers was 57.1% (Example 6) and 85.1% (Example 7), and the uneven distribution of the island components was better induced than in Example 1. The results are shown in Table 1.

[0064] [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.

[0065] The island component diameter CV% of the resulting 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 due to the higher viscosity ratio than in Example 1. The results are shown in Table 1.

[0066] [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.

[0067] By increasing the viscosity ratio compared to Examples 1 and 8, the pressure loss in the flow channel increased and the island component fibers were more likely to aggregate, so the island component diameter CV% of the resulting polymer alloy fiber was 87.2%, and the distribution was better than in Examples 1 and 8. The results are shown in Table 1.

[0068] [Table 1]

[0069] [Comparative Example 1] The flow path design allows for a shear rate of 25 s -1A 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.

[0070] 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% of the obtained polymer alloy fiber was 12.6%, and the cross-sectional morphology was such that it was difficult to say that the uneven distribution of island components, which is a feature of the present invention, was induced. The results are shown in Table 2.

[0071] 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.

[0072] Because 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 component fibers were cut by the high shear, and the island component diameter CV% of the obtained polymer alloy fiber was 18.3%, and the island component fibers were relatively uniformly finely dispersed in the fiber cross section. The results are shown in Table 2.

[0073] 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.

[0074] 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 parts were uniformly and finely dispersed, so the island part diameter CV% of the obtained polymer alloy fiber was 14.8%, and the island parts, which are a feature of the present invention, were not induced very much. The results are shown in Table 2.

[0075] 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.

[0076] 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, so the island part diameter CV% of the obtained polymer alloy fiber was 13.1%, and the island parts, which are a feature of the present invention, were not induced very much. The results are shown in Table 2.

[0077] [Table 2] [Explanation of symbols]

[0078] 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 A: Example of evenly dispersed island components B: Example of an island component with induced uneven distribution

Claims

1. In a channel where the channel length is 10 times or more the channel diameter, a mixture of multiple polymers with a ratio of maximum viscosity to minimum viscosity of 1.5 times or more is passed through the channel at a shear rate of 50 to 3000 s －１ A method for producing synthetic fibers, comprising: causing the material to flow in a fluid atmosphere; and then spinning the material into yarns. The viscosity is a melt viscosity measured at a shear rate of 1216 s −1 .

2. 2. The method for producing synthetic fibers according to claim 1, wherein the length of the flow path is 30 times or more the diameter of the flow path.

3. The shear rate of multiple polymers in the channel is 50 to 1000 s －１ 3. The method for producing synthetic fibers according to claim 1, wherein the

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