Composite spinneret and method for producing sea-island composite fiber using the same

Abstract

To provide a composite spinneret for sea-island composite fibers which can be produced with high productivity while enabling stable cross-section formation without impairing the homogeneity of island components even when a polymer with a large SP value difference is applied, and provide a method for producing the sea-island composite fibers.SOLUTION: There is provided a composite spinneret forming a sea-island cross-section by merging a flow of A polymer and a flow of B polymer from the individual distribution holes and thereafter compressing. The A and B polymer distribution holes in a group of sea-island type distribution holes, in which A polymer distribution hole 9 is surrounded with multiple B polymer distribution holes 10, are drilled to satisfy the following formulae (1), (2) and (3), and the ratio of the number of B polymer distribution holes 12 present outside the group of the sea-island type distribution holes to the number of B polymer distribution holes 11 present in the group of the sea-island type distribution holes is 0.05 or less: LBB' / LAA'≤1.0 (1), LAB / LAA'≥0.5 (2), and 0.25≤D / LAB≤0.70 (3).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a composite spinneret and a method for producing a sea-island composite fiber using the same. [Background technology]

[0002] Currently, the uses of fibers are diversifying, from clothing to industrial materials, and the required characteristics are becoming more diverse, so a wide variety of fiber element technologies have been proposed to meet these demands. Among these technologies, ultra-thin fibers take advantage of the morphological characteristics unique to fiber materials, such as being thin and long, and have a significant effect on the properties when processed into textile products, so various technologies have been disclosed as part of the development of high-performance materials.

[0003] Ultrafine fibers have an increased specific surface area per weight and flexibility, making them a high-value-added textile product that is being used in a wide range of fields, from clothing to industrial materials. By densely arranging ultrafine fibers into nonwoven sheets, they can exhibit a variety of functions, such as the ability to retain chemical solutions due to the uniformly dispersed dense pores, high filtration performance due to the fragmentation of fluids flowing inside the sheet, and the ability to retain encapsulated functional agents for a long period of time, leading to their development as high-performance nonwoven sheets.

[0004] One method for producing ultrafine synthetic fibers is the conjugate spinning method, in which a conjugate fiber having an islands-in-sea cross section is formed by arranging a soluble component as the sea component and a slightly soluble component as the island component, and then the sea component is removed from the conjugate fiber to produce ultrafine fibers composed of the island component. This method is widely adopted industrially from the viewpoints of uniformity of the ultrafine fibers, spinning stability, and productivity.

[0005] Ultrafine fibers produced by the conjugate spinning method are not limited to microfibers with a fiber diameter of a few micrometers as with conventional technology. As the technology becomes more sophisticated, it is now possible to produce nanofibers with extremely small diameters, and the types of materials used have also changed from general-purpose polyesters and polyamides to materials with excellent chemical resistance such as polyolefins.

[0006] Sea-island composite fibers, which are produced by a conjugate spinning method and have island components scattered throughout the sea component, are produced by forming a fiber cross section using a dedicated composite spinneret.

[0007] In the case of a conventional pipe-type sea-island composite spinneret, island component fibers are finely divided by a group of pipes and first formed into a sheath-core composite stream in a sheath-core composite forming hole. Then, the sheath-core composite streams, the number of which corresponds to the number of island components, join together and are compressed in the fiber cross-sectional direction by a tapered discharge plate. The composite fibers are then discharged from the discharge holes to form a fiber with a sea-island composite cross section. In this process, the fiber cross section is significantly compressed by 1 / 500 to 1 / 3000, and the sheath-core composite streams interfere with each other and are compressed. Therefore, it is known that the viscosity and affinity of the polymers to be combined have a significant effect on the formation and stability of the composite cross section.

[0008] Specifically, a combination of polymers with high affinity, such as polyester and copolymer polyester, allows for the production of sea-island composite fibers with relatively high stability over a wide range of conditions, including the viscosity of the combined polymers. On the other hand, a combination of polymers with a large difference in solubility parameters (SP values), such as polyolefin and polyester, is known to cause minute turbulence in the composite flow due to low affinity, making it difficult to control the composite flow in the spinneret, even if the viscosity and other factors are appropriately adjusted, making it difficult to stably produce sea-island composite fibers. In particular, when the number of islands per sea-island composite fiber is increased to reduce the fiber diameter of ultrafine fibers, the control of the core-sheath composite flow corresponding to the increased number of islands and the increase in interfacial tension acting between the components promote this instability, making it difficult to form a good sea-island cross section, as the island components easily bond together.

[0009] To address these issues, Patent Documents 1 and 2 propose technologies for stably producing sea-island composite fibers by specifying the viscosity characteristics and thermal characteristics of the polymers used for the island component and sea component and setting appropriate spinning conditions.

[0010] Furthermore, Patent Document 3 proposes a technology for producing a sea-island composite fiber with excellent island component uniformity by using a characteristic composite spinneret to produce a sea-island composite cross section made of a combination of polymers with low affinity. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Publication No. 2020-26594 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-223190 [Patent Document 3] Japanese Patent Application Laid-Open No. 2000-110028 Summary of the Invention [Problem to be solved by the invention]

[0012] Patent Document 1 discloses that a sea-island composite fiber can be stably produced using a pipe-type sea-island composite spinneret by reducing the difference in melting temperatures between the island component and sea component polymers, even though they have a low affinity. This may potentially suppress cross-section instability caused by the difference in solidification temperatures between the components when the sea-island-shaped polymer composite flow discharged from the spinneret solidifies on the spinning line. However, as described above, conventional pipe-type sea-island composite spinnerets produce unstable polymer composite flows due to minute turbulence in the composite flow caused by low affinity. Therefore, when viewed as a whole, the sea-island composite cross section is partially destabilized, and increasing productivity, such as by increasing the island ratio, can exacerbate this instability and induce cross-section collapse throughout the composite cross section. In other words, it is difficult to say that the fundamental aspects of the pipe-type composite spinneret have been overcome, and there have been cases where the production conditions have been limited by restrictions on spinning conditions and productivity.

[0013] Patent Document 2 describes that in a sea-island composite fiber made of a combination of polymers with a large difference in solubility parameter (SP value), the sea-island composite cross section can be controlled by adjusting the viscosity characteristics of the polymers and by setting the volume ratio of the island component fibers to substantially 50% or less. It is true that increasing the volume ratio of the sea component fibers that make up the sea-island composite cross section can stabilize the sheath-core composite flow formed in the composite spinneret, and as a result, it may be possible to achieve stable formation of a sea-island composite cross section. However, in this case, although bonding between the island component fibers can be suppressed by thickly covering the island component fibers with the sea component fibers, the island component fibers become minor components, which significantly reduces the productivity of ultrafine fibers and may result in inefficient orientation of the fiber structure during the spinning process, resulting in poor fiber properties.

[0014] Patent Document 3 discloses a spinneret technology that can produce sea-island composite fibers with small variation in island component diameters and excellent stability by finely dividing a composite flow discharged as a bonded flow in which island component and sea component fibers are alternately bonded together and then joining the resulting flows together, by utilizing interfacial instability in the melt field resulting from a polymer combination with a large difference in SP value to change the bonded polymer composite flow into an islands-in-sea structure.

[0015] This technology intentionally utilizes the instability of the polymer composite flow caused by low polymer affinity to change the polymer flow from a bonded structure to an islands-in-sea structure. However, because the island components formed are irregularly distributed, the elongation deformation behavior of the fiber becomes unstable, and spinning stability may not be ensured. It is also described that this morphological change of the polymer composite flow requires a residence time in the spinneret of 10 seconds or more, in addition to the polymer affinity, melt viscosity, and sea-island ratio. However, extending the residence time of the polymer composite flow in the spinneret effectively reduces the polymer output, which can sometimes pose a productivity issue in the production of sea-island composite fibers.

[0016] As described above, in sea-island composite fibers composed of a combination of polymers with a large difference in SP value, it is often difficult to achieve both stability of fiber cross section and productivity. For example, there has been a demand for a composite spinneret and production method that can produce sea-island composite fibers using a polyolefin for the island component and a polyester for the sea component without imposing restrictions on spinning conditions or productivity. [Means for solving the problem]

[0017] The above object is achieved by the following means: (1) In a composite spinneret in which a polymer A stream and a polymer B stream from distribution holes for distributing each polymer component are joined together and then compressed to form an islands-in-sea cross section, the polymer A and B distribution holes in an islands-in-sea type distribution hole group in which a polymer A distribution hole is surrounded by a plurality of polymer B distribution holes are drilled so as to satisfy the following formulas (formula 1), (formula 2), and (formula 3), and the ratio of the number of polymer B distribution holes present in the islands-in-sea type distribution hole group to the number of polymer B distribution holes present outside the islands-in-sea type distribution hole group is 0.05 or less. The number of A polymer distribution holes present in the sea-island distribution hole group is 100 or more, and the distance between A and B polymer distribution holes (L AB ) and the number of polymer A distribution holes is 2 × 10 -3 mm / hole or more A composite nozzle. L BB’ / L AA’ ≦1.0 (Formula 1) L AB / L AA’ ≧0.5 (formula 2) 0.25≦D / L AB ≦0.70 (Formula 3) Here, L is the center distance between two polymer distribution holes, and L AA’ is the center-to-center distance between adjacent polymer A distribution holes with the shortest center-to-center distance, L BB’ is the center-to-center distance between adjacent B polymer distribution holes with the shortest center-to-center distance, L AB is the shortest center-to-center distance between adjacent polymer A and polymer B distribution holes. D is the diameter of the polymer distribution holes.

[0019] ( 2 )(1) of A method for producing sea-island composite fibers using a composite spinneret.

[0020] ( 3 ) A polymer is a polyolefin ( 2 10. A method for producing a sea-island composite fiber according to claim 10.

[0021] ( 4 ) B polymer is polyester with a melting point of 230 ° C or higher, and the island ratio calculated by weight ratio is 50% to 90% ( 2 )or( 3 10. A method for producing a sea-island composite fiber according to claim 10.

[0022] is. [Effects of the Invention]

[0023] An object of the present invention is to provide a composite spinneret for producing a sea-island composite fiber, which enables stable cross section formation without impairing the uniformity of island component fibers, an essential feature of a sea-island composite fiber, even when polymers with a large SP value difference are used, and which also enables production with high productivity in industrial use, and a method for producing a sea-island composite fiber using the composite spinneret. [Brief explanation of the drawings]

[0024] [Figure 1] 1A is a front cross-sectional view of the main parts constituting the composite spinneret of the present invention, FIG. 1B is a front cross-sectional view of a part of the distribution plate, and FIG. 1C is a front cross-sectional view of the discharge plate. [Figure 2] 1A and 1B are diagrams relating to a distributor plate of the present invention, in which (a) is a simplified diagram of a group of polymer distribution holes drilled in the lowermost layer of the distributor plate, and (b) is an enlarged view thereof. [Figure 3] 1A and 1B are schematic plan views of polymer distribution hole groups formed in the bottom layer of a distribution plate of the present invention, where (a) is an example of a distribution plate used in an embodiment of the present invention, and (b) is an example of a distribution plate different from the present invention, in which the centers of polymer B distribution holes present in the outermost layer of the sea-island distribution hole groups are connected by straight lines. Note that the distribution holes are partially omitted in the figure (dot pattern portion). DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention will be described in detail below based on preferred embodiments.

[0026] An example of a schematic cross-sectional view of a composite spinneret used in the present invention is shown in Fig. 1. Note that Fig. 1 is a front cross-sectional view, and only two nozzle hole groups each consisting of a group of A polymer nozzles and B polymer nozzles are shown, but the number of nozzle hole groups in the practice of the present invention is not limited.

[0027] The composite spinneret used in the present invention is a composite spinneret for discharging a composite polymer stream composed of polymer A and polymer B, and as shown in FIG. 1 , it is composed of an introduction plate 1 for introducing each polymer component into the distribution plate 2, one or more distribution plates 2 each having distribution holes 5 and / or distribution grooves 4 for distributing each polymer component, and a discharge plate 3.

[0028] The component polymers supplied from the inlet plate 1 pass through the distribution grooves 4 and / or distribution holes 5 of at least one laminated distributor plate 2, and then join together to form a composite polymer stream. The composite polymer stream then passes through the discharge inlet holes 6 and reduction holes 7 of the discharge plate 3 and is discharged from the spinneret discharge holes 8 to produce fibers.

[0029] Here, the principle that the sea-island composite cross section with excellent island component uniformity can be stably formed and that high-level productivity can be achieved even when a polymer with low affinity is used, which is a fundamental problem in the production methods of the prior art, is described below. This is an important point for achieving the object of the present invention.

[0030] It is generally known that when two polymers are brought into contact in the molten state, the molecular chains penetrate each other and form entanglements at the polymer interface, stabilizing the composite polymer morphology. However, when molten polymers with low affinity are brought into contact, the penetration and entanglement of the molecular chains at the polymer interface is hindered, causing instability at the polymer interface. This instability results in a large interfacial tension that minimizes the interfacial energy, resulting in a distorted and unstable composite polymer morphology. This phenomenon can significantly impair the stability of the fiber cross section during melt spinning when polymers with low affinity are combined, which can be particularly fatal in sea-island composite fibers formed by the aggregation of many fine polymer streams.

[0031] As a result of extensive investigations into the above-mentioned problems, the present inventors have found an arrangement pattern of island component holes and sea component holes that significantly improves the cross-sectional stability, which has been a problem in the conventional techniques.

[0032] That is, the composite spinneret is configured so that, in the distribution holes 5 in the lowest layer of the distributor plate 2 (the holes for discharging the A polymer are called the A polymer distribution holes 9, and the holes for discharging the B polymer are called the B polymer distribution holes 10), the A and B polymer distribution holes in an islands-in-sea type distribution hole group, where a plurality of B polymer distribution holes 10 surround an A polymer distribution hole 9, satisfy formulas 1 and 2, and the ratio of the number of B polymer distribution holes present in the islands-in-sea type distribution hole group to the number of B polymer distribution holes present outside the islands-in-sea type distribution hole group is 0.05 or less. It has been found that the use of this composite spinneret makes it possible to achieve both stability and productivity, which was previously difficult to achieve. Note that the distribution holes 5 in the lowest layer of the distributor plate 2 here refer to the distribution holes perforated in the distributor plate 2 located immediately above the discharge plate 3.

[0033] Hereinafter, in the present invention, unless otherwise clearly stated, the A polymer corresponds to the island component and the B polymer corresponds to the sea component.

[0034] The "islands-in-the-sea type distribution hole group" in the present invention refers to an aggregate of distribution holes in the lowest distribution hole 5 of the distributor plate 2, through which each polymer stream passes when being discharged from the distributor plate 2 toward the discharge introduction hole 6, in which a plurality of distribution holes 10 of polymer B are provided so as to surround one distribution hole 9 of polymer A.

[0035] That is, when the distribution holes 5 in the lowermost layer of the distribution plate 2 are formed with polymer A distribution holes 9 and polymer B distribution holes 10 as shown in FIG. 2(a), the collection of polymer A and B distribution holes present in the region surrounded by dashed line 11 is called an "islands-in-the-sea type distribution hole group," and polymer B distribution holes present in the region corresponding to dashed line 12 are called "polymer B distribution holes present outside the islands-in-the-sea type distribution hole group."

[0036] In the composite spinneret of the present invention, both polymer streams of polymer A and polymer B are discharged simultaneously from the distribution holes 5 in the lowest layer of the distributor plate 2 toward the discharge introduction holes 6, and each polymer stream flows along the polymer spinning path while expanding in a direction perpendicular to the direction of the polymer's spinning path, and the two polymers join to form a composite polymer stream. The discharge introduction holes 6 are used to direct the composite polymer stream perpendicular to the discharge surface for a certain distance, and are intended to reduce the flow velocity distribution in the cross-sectional direction of the composite polymer stream and improve stability.

[0037] Thus, since the A polymer and B polymer streams join for the first time at the discharge introduction hole 6 to form an islands-in-the-sea composite polymer stream, it is necessary that multiple B polymer distribution holes are arranged to surround one A polymer distribution hole. In addition, in order to achieve the intended effects of the present invention, the stability of the composite polymer morphology at the discharge introduction hole 6 is an important factor. To ensure the stability of such composite polymer morphology, the arrangement of the A polymer distribution holes 9 and the B polymer distribution holes 10 drilled in the lowest layer of the distributor plate 2, which is responsible for forming the cross section, is important. That is, in the present invention, it is required that the A polymer distribution holes 9 and the B polymer distribution holes 10 are drilled in the lowest layer of the distributor plate 2 so as to satisfy the following (Equations 1), (Equation 2), and (Equation 3).

[0038] FIG. 2(b) shows a partially enlarged view of an example of the polymer distribution holes (FIG. 2(a)) that correspond to the islands-in-the-sea type distribution hole group. L BB’ / L AA’ ≦1.0 (Formula 1) L AB / L AA’ ≧0.5 (formula 2) 0.25≦D / L AB ≦0.70 (Formula 3) Here, L is the center distance between two polymer distribution holes, and L AA’ is the center-to-center distance between adjacent polymer A distribution holes with the shortest center-to-center distance, L BB’ is the center-to-center distance between adjacent B polymer distribution holes with the shortest center-to-center distance, L ABis the shortest center-to-center distance between adjacent polymer A and polymer B distribution holes. D is the diameter of the polymer distribution holes.

[0039] In formula 1, this means that the center-to-center distance between adjacent B polymer distribution holes is equal to or less than the center-to-center distance between adjacent A polymer distribution holes. By arranging the distribution holes 5 in the lowest layer in this way, the polymer discharged from each distribution hole expands in the direction perpendicular to the spinning path direction at the discharge introduction holes 6, and in the process of the polymer streams joining, the joining of B polymer streams with a close center-to-center distance is prioritized, resulting in a composite polymer form in which the B polymer completely surrounds the A polymer, thereby exerting the effect of greatly suppressing the joining of A polymer streams. In other words, L BB’ / L AA’ The smaller the distance between the centers of adjacent B polymer distribution holes, the more pronounced this effect will be. However, if the distance between the centers of adjacent B polymer distribution holes is too short, the B polymer streams discharged from the distribution holes will join and then widen, which may cause cross-sectional instability as distorted polymer streams. In addition, in consideration of the processing restrictions when drilling the distribution holes, it is necessary to consider the L BB’ / L AA’ The practical lower limit is 0.25.

[0040] In formula 2, the center-to-center distance between adjacent polymer A distribution holes 9 and polymer B distribution holes 10 is at least 0.5 times the center-to-center distance between adjacent polymer A distribution holes. Considering that polymer A distribution holes 9 are surrounded by polymer B distribution holes 10, the practical upper limit is less than 1.0.

[0041] In the process of forming a composite polymer by joining polymer A and polymer B at discharge introduction hole 6, it is important that the two polymers join in a state where the cross-sectional flow of each polymer is relaxed so that the two polymers join without disrupting the polymer interface. From this perspective, by drilling polymer A and polymer B distribution holes so as to satisfy formula 2, polymer A and polymer B discharged from the distribution holes will join with their cross-sectional flow relaxed at discharge introduction hole 6, and a composite polymer can be formed without disrupting the polymer interface.

[0042] In addition, based on the above viewpoint, it is also important to control the width of the A polymer and B polymer streams in the cross-sectional direction immediately after they are discharged from each polymer distribution hole in order to form a stable cross-sectional shape. As shown in Equation 3, the width of the A polymer and B polymer distribution hole (D) and L AB The ratio of D / L AB By setting this ratio to 0.25 or more, excessive widening of the polymer flow due to an excessively small hole diameter is suppressed, and a stable composite polymer flow can be formed without unnecessarily disturbing the composite polymer interface between the A polymer and the B polymer. For this reason, the larger this ratio is, the more stable the cross section formation becomes. However, from the viewpoint of stable production of sea-island composite fibers, which is also the intended effect of the present invention, taking into account discharge stability from the polymer distribution holes and the arrangement of a large number of A polymer distribution holes, the upper limit is 0.70. Note that, in the polymer distribution holes corresponding to the sea-island distribution hole group, when the distribution holes are formed so as to satisfy formulas 1, 2, and 3, the B polymer distribution holes 10 are formed substantially uniformly around the circumference of a circle centered on the A polymer distribution hole 9.

[0043] The polymers discharged from the distribution holes 5 satisfying the above conditions and joined at the discharge introduction hole 6 flow into the contracting hole 7 as a precisely controlled islands-in-the-sea composite polymer stream and are contracted in the cross-sectional direction. In this case, the streamline of the polymer stream located in the middle layer of the cross section is almost straight, whereas the polymer streams in the outer layers are significantly bent toward the center of the cross section, causing interference between the polymer streams near the outer layers. This interference between polymer streams is a sufficient cause of instability in combinations of polymers with low affinity. Therefore, in the present invention, it is required that the ratio of the number of polymer B distribution holes present outside the islands-in-the-sea type distribution hole group to the number of polymer B distribution holes present in the islands-in-the-sea type distribution hole group be 0.05 or less.

[0044] This means that, among the B polymer distribution holes 10 drilled in the distributor plate 2, the ratio of the number of B polymer distribution holes that do not belong to the islands-in-sea type distribution hole group to the number of B polymer distribution holes that belong to the islands-in-sea type distribution hole group is very small. Generally, the B polymer distribution holes 10 that do not belong to the islands-in-sea type distribution hole group, located at the outermost periphery, are positioned to completely cover the outer layer of the composite polymer flow with the B polymer. This is expected to ensure uniform shear stress due to contact with the hole walls in the circumferential direction, thereby ensuring spinning stability. However, in polymer combinations with low affinity, the polymer flow in the outer layer that does not contribute to cross-section formation may bend significantly toward the center of the cross-section, causing interference with unnecessary polymer flows. In other words, we discovered that suppressing the instability of the composite polymer flow induced after the discharge introduction hole 6 in conventional technology leads to significant improvements in cross-section formability and spinning stability.

[0045] When this technical concept is pursued, it is preferable to minimize the number of B polymer distribution holes 10 that do not fall into the islands-in-sea type distribution hole group, and by setting the number of B polymer distribution holes that do not fall into the islands-in-sea type distribution hole group as in the present invention, the composite polymer flow can be discharged from the spinneret discharge hole 8 without impairing its stability even during the compression process in the reduction hole 7. For this reason, in the present invention, it is possible to produce sea-island composite fibers with excellent cross-sectional stability even when polymers with low affinity are combined.

[0046] As described above, in the composite spinneret of the present invention, by optimizing the distribution holes 5 in the lowermost layer of the distributor plate 2, even when the polymers have low affinity with each other, it is possible to suppress destabilization during the polymer joining process at the discharge introduction holes 6 and the compression process at the reduction holes 7, and it is possible to stably produce sea-island composite fibers without substantially restricting the spinning conditions or productivity.

[0047] Generally, in a sea-island composite spinneret, increasing the number of island filaments in a single filament is advantageous in terms of improving the productivity of sea-island composite fibers and increasing the fiber diameter. From this perspective, also in the composite spinneret of the present invention, the more the number of polymer A distribution holes drilled in the distributor plate 2, which corresponds to the number of island filaments, the better, and the number of polymer A distribution holes is preferably 100 or more to reasonably achieve the intended effects of the present invention.

[0048] On the other hand, if the number of A polymer distribution holes 9 is excessively large, the distance between A and B polymer distribution holes (L AB In this case, in the process of joining polymer A and polymer B at the discharge introduction hole 6, they join immediately after the polymers are discharged from the distribution hole 5 in the lowest layer, and a composite polymer flow is formed in a state in which the flow of each polymer in the cross-sectional direction cannot be fully relaxed, which may destabilize the polymer interface and promote poor cross-sectional formation. Therefore, it is necessary to reduce the distance between the A and B polymer distribution holes (L AB ) and the number of polymer A distribution holes is 2.0 × 10 -3Within this range, very stable sea-island composite fibers can be produced with high productivity, and from this perspective, the substantial upper limit of the number of A polymer distribution holes is 100,000.

[0049] The holes formed in the inlet plate 1, distributor plate 2, and discharge plate 3 of the composite spinneret of the present invention are preferably processed so that their cross-sectional areas are constant, and this may be appropriately selected from conventionally known metal cutting processes, etc., in consideration of processing conditions, etc. "Constant" here means that the cross-sectional area of ​​each hole is within a range of ±10%, and as long as it is within this range, it is possible to produce a sea-island composite fiber without impairing the intended effects of the present invention. The inlet plate 1, distributor plate 2, and discharge plate 3 that have been processed to have holes in this way are stacked in this order to form the composite spinneret of the present invention. The shape of the composite spinneret in the present invention may be circular, rectangular or polygonal, and may be appropriately selected depending on the specifications of the spinning machine to be used. Next, the method for producing a sea-island composite fiber using the composite spinneret of the present invention will be described in detail.

[0050] The following describes the process of polymer flow from upstream to downstream of the composite spinneret shown in FIG. 1 , from when the composite polymer flows through introduction plate 1 and distributor plate 2 to when the composite polymer flow is discharged from the spinneret discharge holes in discharge plate 3.

[0051] Polymer A and polymer B flow separately into introduction plate 1 from the upstream of the spin pack and then flow separately into distribution grooves 4 of distributor plate 2. Distributor plate 2 has distribution grooves 4 for storing the polymers that flow in, and distribution holes 5 drilled in the lower surface of these distribution grooves for allowing the polymers to flow downstream.

[0052] The cross-sectional morphology of the sea-island composite fiber can be controlled by the arrangement of the distribution holes 5 in the lowest layer of the distributor plate 2. In this case, to increase the precision of the cross-sectional morphology, the A polymer and the B polymer are distributed to an extremely large number of the distribution holes 5 in the lowest layer of the distributor plate 2, so that the throughput per distribution hole is extremely small and the pressure loss across the distribution holes is also reduced to 10%. -2 From 10 -5MPa level, the polymer streams discharged from each distribution hole are easily interfered with by other polymer streams. Therefore, in order to suppress the interference between the polymers, it is preferable to adjust the hole diameters of the A polymer distribution holes 9 and the B polymer distribution holes 10 and control the discharge speed of the polymer streams discharged from each distribution hole. The preferred range of the flow rate ratio is when the discharge speed F of the A polymer per distribution hole is A , B is the polymer extrusion speed, F is B If so, the ratio (F A / F B Or F B / F A ) is preferably 0.05 to 20, more preferably 0.1 to 10. Within this range, the polymers discharged from the distribution holes 5 in the lowermost layer of the distributor plate 2 do not interfere with each other, and the composite polymer flow is guided as a laminar flow to the reduction hole 7 via the discharge introduction hole 6, so that the cross-sectional shape is stable and can be maintained with precision.

[0053] The composite spinneret of the present invention is characterized by its ability to stably produce sea-island composite fibers without imposing any restrictions on the polymers to be combined, and is particularly effective in combinations of polymers with large differences in solubility parameters (SP value differences), which can result in unstable formation of composite cross sections when using conventional spinnerets.

[0054] The SP value here is (evaporation energy / molar volume) 1 / 2 SP is a parameter that reflects the cohesive strength of a substance, and the closer these values ​​are, the higher the affinity and compatibility of the polymer combination. This SP value is known for various polymers, and is listed, for example, on page 189 of the "Plastics Data Book" (co-edited by Asahi Kasei Amidas Co., Ltd. and the Plastics Editorial Department, 1999).

[0055] In the present invention, a polymer combination with a large SP value difference is one in which the absolute value of the difference in SP value is 2 (MJ / m 3 ) 1 / 2The larger this value, the lower the affinity of the polymer combination.

[0056] In this case, the penetration and entanglement of molecular chains is hindered at the interface of the polymers that come into contact in a molten state, and the instability that occurs at the polymer interface makes it more likely to cause poor cross-section formation. Therefore, in view of the objective effects of the present invention, the difference in SP value between the two types of polymers should be 2 to 7 (MJ / m) in absolute value. 3 ) 1 / 2 is a preferable range in that the composite spinneret of the present invention exhibits its effects.

[0057] In particular, selecting a polymer combination with a large SP value difference leads to a large difference in the melting points of the polymers, which can improve the heat resistance of the sea-island composite fiber, for example, and is expected to provide excellent processability. Therefore, it is recommended to select a polymer combination with a SP value difference of 4 to 7 (MJ / m 3 ) 1 / 2 A more preferable range is as follows.

[0058] From the above viewpoints, examples of island component polymers for the sea-island composite fiber produced by the composite spinneret of the present invention include polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyolefin, polyamide, thermoplastic polyurethane, polyphenylene sulfide, polyarylate, and copolymers thereof. Among these, the island component polymer may be selected based on compatibility with other fibers in the fiber sheet to be used as ultrafine fibers, and the mechanical properties, heat resistance, chemical resistance, and other properties that are ultimately required. For example, for applications requiring chemical resistance, such as papermaking sheets applicable to battery separators, polyolefin, polyphenylene sulfide, and the like are more preferred because of their high crystallinity.

[0059] The sea component polymer of the sea-island composite fiber produced by the composite spinneret of the present invention is preferably selected from melt-processable polymers (easily soluble polymers) that are more soluble in solvents such as alkaline solutions than the island component polymers, such as polyesters and their copolymers, polylactic acid, polyamide, polystyrene and its copolymers, polyethylene, and polyvinyl alcohol. The soluble polymer referred to here is preferably one whose dissolution rate ratio (=dissolution rate of the soluble polymer / dissolution rate of the sparingly soluble polymer) is 100 or more in the solvent used for dissolution treatment, when the sparingly soluble polymer (island component) is used as the reference. To simplify the dissolution treatment and prevent unnecessary deterioration of the island component fibers by the solvent, it is preferable to select a polymer whose dissolution rate ratio is 3000 or more.

[0060] From the above viewpoints, taking into account the balance between the production stability of sea-island composite fibers and the difference in polymer melting points and SP values, it is preferable that the polymers applied to the present invention be a combination of polyolefin for the island components and polyester for the sea component. In addition, from the viewpoints of handleability and processability, it is more preferable to use polypropylene for the island components and polyester for the sea component, and for the purpose of improving the solubility of the sea component polymer without impairing processability, it is even more preferable to use polyethylene terephthalate for the sea component, or polyethylene terephthalate into which a copolymerization component has been introduced so that the melting point is 230°C or higher.

[0061] These polymers may 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, within the scope of the present invention.

[0062] Furthermore, in the polymers constituting the sea-island composite fiber produced by the composite spinneret of the present invention, the melt viscosity ratio between the melt viscosity of polymer A and the melt viscosity of polymer B is preferably 0.1 to 5.0. In the present invention, the cross-sectional morphology of the composite fiber is basically controlled by the arrangement of the distribution holes 5 in the lowest layer, but after the individual polymers join together to form a composite polymer stream, the stream is significantly reduced in the cross-sectional direction by the reduction hole 7. For this reason, the melt viscosity ratio at that time, i.e., the rigidity ratio of the molten polymers, may affect the formation of the cross section. For this reason, a melt viscosity ratio of 0.3 to 3.0 is more preferable.

[0063] The melt viscosity here is the value measured in a nitrogen atmosphere using a melt viscosity measuring device that can change the strain rate stepwise after reducing the moisture content of chip-shaped polymer to 200 ppm or less using a vacuum dryer. The melt viscosity measurement temperature is the same as the spinning temperature, and the strain rate is 121.6 s -1 The melt viscosity of the polymer was determined as follows: The melt viscosity of each polymer was measured individually, the viscosity ratio was calculated as polymer A / polymer B, and the value was rounded to one decimal place.

[0064] The composite polymer stream discharged from the distributor plate 2 flows into the discharge plate 3. Here, the discharge plate 3 is preferably provided with discharge introduction holes 6. The discharge introduction holes 6 are intended to allow the composite polymer stream discharged from the distributor plate 2 to flow perpendicular to the discharge surface for a certain distance. The purpose of these holes is to reduce the difference in flow velocity between polymer A and polymer B and to reduce the flow velocity distribution in the cross-sectional direction of the composite polymer stream. In the present invention, the provision of these discharge introduction holes 6 is advantageous from the viewpoint of stabilizing the morphology of the composite polymer.

[0065] In terms of suppressing this flow rate distribution, it is preferable to control the flow rate of each polymer by adjusting the discharge rate, hole diameter, and number of holes in the distribution holes 5 of the lowest layer of each polymer. From the viewpoint of almost completing the relaxation of the flow rate ratio, it is preferable to control the flow rate of each polymer by adjusting the discharge rate, hole diameter, and number of holes in the distribution holes 5 of the lowest layer of each polymer. -1It is preferable to design the discharge introduction hole 6 with a target value of about 10 seconds (=discharge introduction hole length / polymer flow rate).Within this range, the distribution of flow rate is sufficiently alleviated, which is effective in improving the stability of the cross section.

[0066] Next, the composite polymer stream is reduced in the cross-sectional direction along the polymer flow by reduction hole 7 while being introduced into the discharge hole having a desired diameter. Here, the streamline of the composite polymer stream in the middle layer is almost straight, but as it approaches the outer layer, it becomes more curved. In order to produce the sea-island composite fiber of the present invention, it is preferable to reduce the composite polymer stream composed of countless polymer streams of polymer A and polymer B without destroying the cross-sectional form of the composite polymer stream. For this reason, it is preferable to set the angle of the hole wall of this reduction hole 7 to the discharge surface in the range of 30° to 90°.

[0067] As described above, the composite polymer stream passes through the discharge introduction hole 6 and the reduction hole 7, maintaining a cross-sectional shape based on the arrangement of the distribution holes 5 in the lowest layer, and is discharged from the spinneret discharge hole 8 to the spinning line. The purpose of this spinneret discharge hole 8 is to re-meter the flow rate of the composite polymer stream, i.e., the discharge rate, and to control the draft (=take-up speed / discharge linear speed) on the spinning line, which will be described later. The hole diameter and hole length of the spinneret discharge hole 8 are preferably determined taking into consideration the viscosity of the polymers and the discharge rate. When producing the composite fiber of the present invention, it is preferable to select the discharge hole diameter D from 0.1 to 2.0 mm and the L / D (discharge hole length / discharge hole diameter) from the range of 0.1 to 5.0.

[0068] The spinning temperature in the production method of the present invention is preferably set to a temperature at which, among the polymers used and determined from the above-mentioned viewpoints, mainly polymers with high melting points or high viscosity exhibit fluidity. The temperature at which this fluidity is exhibited varies depending on the polymer properties and molecular weight, but the melting point of the polymer serves as a guide, and the temperature may be set to a temperature not higher than 60°C above the melting point of the high-melting polymer. If the temperature is below this level, the polymer will not undergo thermal decomposition or the like in the spinning head or spin pack, and a decrease in molecular weight will be suppressed, allowing for good production of composite fibers.

[0069] In the production method of the present invention, the polymer extrusion rate can be in the range of 0.1 g / min / hole to 20.0 g / min / hole per nozzle, allowing for 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 determined based on the relationship between the melt viscosity of the polymer, the nozzle diameter, and the nozzle length.

[0070] The island component ratio when spinning the composite fiber used in the production method of the present invention is preferably selected in the range of 50 to 90% by weight based on the throughput rate. Within this range, sea-island composite fibers can be produced efficiently and stably while maintaining the stability of the composite cross section. From the viewpoint of further improving productivity, the island component ratio converted into a weight ratio is more preferably 60 to 90%, and even more preferably 70 to 90%.

[0071] The molten polymer stream discharged from the spinneret discharge holes 8 is cooled and solidified, and then focused by adding an oil or the like, and taken up by rollers with a specified peripheral speed. This take-up speed is determined based on the discharge rate and the desired fiber diameter. In the present invention, from the viewpoint of stably producing a sea-island composite fiber, the roller take-up speed is preferably about 500 to 6,000 m / min, and can be changed depending on the physical properties of the polymer and the intended use of the fiber.

[0072] In this case, a spinning draft of 300 times or less is preferred because uniform fibers with reduced variations in physical properties among the yarns can be produced. The spinning draft of the sea-island composite fiber, represented by the following formula, is preferably 50 to 300. Spinning draft = Vs / V0 Here, Vs is the spinning speed (m / min), and V0 is the linear extrusion speed (m / min).

[0073] By setting the spinning draft to 50 or more, it is possible to prevent the polymer flow discharged from the spinneret discharge holes 8 from remaining directly below the spinneret for a long period of time, thereby suppressing contamination of the spinneret surface and stabilizing spinnability. Furthermore, by setting the spinning draft to 300 or less, it is possible to suppress yarn breakage due to excessive spinning tension, and it is preferable to produce sea-island composite fibers with stable spinnability. For this reason, it is more preferable that the spinning draft is 80 to 250.

[0074] Here, it is preferable to draw the spun sea-island composite fiber from the viewpoints that not only can the mechanical properties be improved by promoting the uniaxial orientation of the fibers but also that thermal dimensional stability can be imparted to the spun sea-island composite fiber during advanced processing, etc. Regarding drawing, the spun sea-island composite fiber may be drawn after being temporarily wound up, or may be drawn immediately after spinning without being temporarily wound up.

[0075] As for the drawing conditions, for example, in a drawing machine consisting of one or more pairs of rollers, fibers made of a polymer exhibiting thermoplasticity that can generally be melt-spun are naturally drawn in the fiber axis direction, heat-set, and wound up by using a peripheral speed ratio between the first roller set at a temperature above the glass transition temperature and below the melting point and the second roller set at a temperature equivalent to the crystallization temperature. Here, heating with a heated roller is used as an example, but drawing may also be performed in steam or hot water. For polymers that do not exhibit a glass transition, the dynamic viscoelasticity (tan δ) of the sea-island composite fiber is measured, and a temperature equal to or higher than the peak temperature on the higher side of this tan δ may be selected as the preheating temperature. From the viewpoints of increasing the draw ratio and improving the mechanical properties and processability, it is also preferable to perform this drawing process in multiple stages.

[0076] To convert the sea-island composite fiber thus produced into ultrafine fibers, the composite fiber is immersed in a solvent capable of dissolving the readily soluble component to remove the readily soluble component, resulting in ultrafine fibers composed of the slightly soluble component. When the readily soluble component is polyethylene terephthalate, a copolymer in which 5-sodium sulfoisophthalic acid or the like is copolymerized, or polylactic acid (PLA), an alkaline aqueous solution such as a sodium hydroxide aqueous solution can be used. For example, the sea-island composite fiber may be treated with an alkaline aqueous solution by immersing the sea-island composite fiber or a fiber structure made from the same in the alkaline aqueous solution. Heating the alkaline aqueous solution to 50°C or higher is preferred because it accelerates the progress of hydrolysis. Furthermore, using a fluid dyeing machine or the like for treatment allows for large quantities to be processed at once, improving productivity and making it preferable from an industrial perspective.

[0077] As described above, the method for producing a sea-island composite fiber using the composite spinneret of the present invention has been explained based on a general melt spinning method. However, it goes without saying that the sea-island composite fiber can also be produced by a melt-blowing method or a spunbonding method, and further, it is also possible to produce the sea-island composite fiber by a solution spinning method such as a wet method or a dry-wet method. [Example]

[0078] The composite spinneret of the present invention and the sea-island composite fibers produced by the composite spinneret will be specifically described below with reference to examples. The examples and comparative examples were evaluated as follows.

[0079] A. Center-to-center distance of polymer distribution holes (L AA’、 L BB’、 L AB ), polymer distribution pore size (D) When the composite spinneret in each Example and Comparative Example was a distributor-type spinneret, an image of the polymer distribution hole group drilled in the bottom layer of the distributor plate was taken with a digital microscope manufactured by KEYENCE Corporation at a magnification that included 10 or more distribution holes. The center-to-center distance and distribution hole diameter of each polymer distribution hole were measured using image processing software (WINROOF), and the values ​​rounded to two decimal places were defined as the center-to-center distance (L) and distribution hole diameter (D), respectively.

[0080] BA and B polymer distribution hole count When the composite spinneret in each Example and Comparative Example is a distributor spinneret, the polymer distribution hole group drilled in the bottom layer of the distribution plate is photographed with a KEYENCE digital microscope at a magnification that includes all distribution holes, and the number of polymer distribution holes A (N A Next, the centers of the polymer B distribution holes present in the outermost layer of the sea-island distribution hole group are connected by a straight line, and the number of polymer B distribution holes included within the straight line is counted as "polymer B distribution holes present in the sea-island type distribution hole group" (N B1 ), and the number of polymer B distribution holes not included in the line is counted as "polymer B distribution holes existing outside the sea-island type distribution hole group" (N B2 ) is counted as

[0081] C. Polymer melt viscosity and viscosity ratio The polymer chips were dried in a vacuum dryer to a moisture content of 200 ppm or less, and the melt viscosity was measured by a Toyo Seiki Capillograph at a strain rate of 121.6 s. The measurement temperature was the same as the spinning temperature, and the time from the sample being placed in the heating furnace under a nitrogen atmosphere to the start of the measurement was 5 minutes. -1 The melt viscosity of the polymer was evaluated as the melt viscosity of the polymer. Furthermore, the melt viscosity of polymer A was divided by the melt viscosity of polymer B, and the value was rounded to two decimal places to obtain the viscosity ratio (polymer A / polymer B).

[0082] D. Fineness The weight of 100m of fiber was measured and multiplied by 100 to calculate the value. This process was repeated 10 times, and the average value was rounded to one decimal place to obtain the total fineness (dtex). The value obtained by dividing the total fineness by the number of filaments is the single fiber fineness (dtex).

[0083] E. Cross-section formability (island component diameter variation) The produced sea-island composite fibers were embedded in epoxy resin, frozen using a Reichert FC-4E cryosectioning system, and cut using a Reichert-Nissei Ultracut N (ultramicrotome) equipped with a diamond knife. The cut surfaces were then photographed using a transmission electron microscope (TEM) at a magnification that allowed observation of all island components within a single sea-island composite fiber for 10 different sea-island composite fibers. From these images, the island component diameters of all 10 sea-island composite fibers were measured using WINROOF, and the average and standard deviation were calculated. From these results, the fiber diameter CV% was calculated using the following formula, and cross-section formability was judged based on the following: Island component diameter variation (CV%) = (standard deviation / average value) x 100 Good A: Island component diameter variation <20.0 Poor C: Island component diameter variation ≧ 20.0.

[0084] F. Spinning stability Spinning and drawing were carried out for each example, and the spinning stability was evaluated based on the number of thread breaks per 1 million meters, on the following three-point scale. Good A: Number of thread breakages < 1.0 times / million meters Acceptable B: 1.0 times / million m≦Number of thread breakages<2.0 times / million m Poor C: Number of yarn breakages ≥ 2.0 times / million m.

[0085] [Example 1] The composite spinneret is arranged as shown in Figure 3(a), and L BB’ / L AA’ =0.58, L AB / L AA’ =0.58, D A / L AB , D B / L AB=0.46, N B2 / N B1 =0, N A =100, L AB / N A =3.5×10 -3 A distribution plate having A and B polymer distribution holes drilled in the bottom layer so as to fill the gap (mm / hole) was used.

[0086] The A polymer was polypropylene (PP1, melting point: 162°C, melt viscosity: 72 Pa s), and the B polymer was polyethylene terephthalate (PET1, melting point: 260°C, melt viscosity: 63 Pa s). The melt viscosity ratio of these polymers (polymer A / polymer B) was 1.1, and the SP difference was 5.3 (MJ / m 3 ) 1 / 2 After melting both polymer A and polymer B at 260°C and 280°C, respectively, using an extruder, the spinning temperature was set to 280°C so that the extrusion rates of polymer A and polymer B were in a weight ratio of 70 / 30, and the polymers were fed into a composite spinneret, from which a composite polymer stream was extruded from the extrusion holes.

[0087] The composite polymer stream discharged from the nozzle was cooled and solidified, then an oil was added and the stream was wound up at a spinning speed of 1000 m / min to produce an undrawn fiber. The undrawn fiber was then drawn 2.6 times between rollers heated to 85°C and 130°C, producing a sea-island composite fiber of 72 dtex-36 filaments (single fiber fineness 2.0 dtex) through the spinning and drawing process.

[0088] This sea-island composite fiber had a high island component weight ratio of 70%, but the island components were uniformly present, the island component diameter variation was 5.6%, and the cross section formability was very good. The number of yarn breakages in the spinning and drawing processes was 0 times per million meters, and the fiber had extremely good spinning stability. The results are shown in Table 1.

[0089] [Comparative Example 1] As shown in Figure 3(b), a composite spinneret was used, in which the distribution holes for polymer B were drilled so as to cover the outermost periphery of the distribution plate (N B2 / N B1A sea-island composite fiber was produced in the same manner as in Example 1, except that the cellulose acylate copolymer (CuO 2 ) was used.

[0090] In the produced sea-island composite fiber, random bonding between island component fibers was observed in multiple locations due to instability caused by interference of polymer flows caused by large bending in the reduction hole of polymer flows in the outer layer that did not contribute to cross section formation. As a result, the uniformity of the island component fibers was impaired, and the cross section formability was inferior to that of Example 1. Furthermore, with regard to spinning stability, although no yarn breakage was observed in the spinning process, yarn breakage due to non-uniformity of the cross section occurred in the drawing process, and the spinning stability was also inferior to that of Example 1. The results are shown in Table 1.

[0091] Comparative Example 2 As a composite nozzle, L BB’ / L AA’ =1.73, L AB / L AA’ A sea-island composite fiber was produced by the same procedure as in Example 1, except that a distribution plate having polymer distribution holes perforated therein so that the viscosity of the polymer blended with the polymer content ...

[0092] The produced sea-island composite fiber had prominent bonding between two island component fibers, due to the fact that the center-to-center distance between the A polymer distribution holes in the lowermost layer of the distributor plate was closer than that between the B polymer distribution holes, which promoted merging of the A polymers and resulted in poorer cross section formability than in Example 1. Furthermore, yarn breakage occurred in the drawing step due to non-uniformity of the cross section, and spinning stability was also poorer than in Example 1. The results are shown in Table 1.

[0093] Comparative Example 3 A sea-island composite fiber was produced by performing everything as described in Example 1, except that a conventionally known pipe-type sea-island composite spinneret (number of island fibers: 100) was used as the composite spinneret.

[0094] The produced sea-island composite fiber had a high island ratio, which promoted the formation of an unstable polymer composite flow due to fine turbulence of the composite flow caused by low affinity, resulting in large island mergers and the formation of a proper sea-island cross section. As a result, the island component diameter variation was much larger than in Example 1, and yarn breakage occurred frequently during the spinning and drawing processes. The results are shown in Table 1.

[0095] [Examples 2 and 3] In Example 2, L BB’ / L AA’ =1.00, L AB / L AA’ In Example 3, L BB’ / L AA’ =0.27, L AB / L AA’ A sea-island composite fiber was produced according to the procedure of Example 1, except that a distributor plate having distribution holes for polymer B perforated in the lowermost layer of the distributor plate so that the viscosity of polymer B was 0.52 was used.

[0096] All of the sea-island composite fibers exhibited good cross-section formability and island component uniformity, but in particular, L BB’ / L AA’ and L AB / L AA’ Example 3, in which the value of is minimized, exhibited better island component uniformity than Example 1. The results are shown in Table 1.

[0097] [Examples 4 and 5] Sea-island composite fibers were produced according to Example 1, except that the number of polymer A distribution holes drilled in the lowermost layer of the distribution plate was changed to 200 (Example 4) or 500 (Example 5).

[0098] The produced sea-island composite fibers maintained island component uniformity and had good cross section formability even when the number of island components was increased, and were sea-island composite fibers that could be made into ultrafine fibers even thinner than those of Example 1. The results are shown in Table 1.

[0099] [Examples 6 to 9] In Examples 6 to 9, sea-island composite fibers were produced as in Example 1, except that the discharge rate of polymer A was kept constant and the discharge rate of polymer B was changed so that the weight ratio of polymer A was 50, 60, 80, or 90%.

[0100] The sea-island composite fibers produced in Examples 6 and 7 had a higher ratio of the sea part compared to Example 1, which promoted stabilization of the composite polymer flow in the spinneret, and therefore showed better island part uniformity compared to Example 1. The sea-island composite fibers produced in Examples 8 and 9 had excellent cross section formability and spinning stability despite their high island component ratios, and were superior in productivity compared to Example 1. The results are shown in Table 2.

[0101] [Examples 10 and 11] Sea-island composite fibers were produced as in Example 1, except that in Example 10, polyethylene terephthalate (PET2, melt viscosity: 200 Pa s) was used as the B polymer, and in Example 11, polyethylene terephthalate copolymerized with 8.0 mol % of 5-sodium sulfoisophthalic acid and 10 wt % of polyethylene glycol having a molecular weight of 1,000 (copolymerized PET, melt viscosity: 184 Pa s) was used as the B polymer.

[0102] The sea-island composite fiber produced in Example 10 exhibited relatively good cross section formability even when the polymer viscosity ratio was small.

[0103] The sea-island composite fiber produced in Example 11 had a small polymer viscosity ratio, but a small melting point difference. Therefore, when the polymer composite stream discharged from the spinneret solidified on the spinning line, cross-section instability caused by the difference in solidification temperature between the components was suppressed, and the resulting fiber had extremely good cross-section formability. Furthermore, the introduction of the copolymer component provided excellent alkali elution, which was superior to that of Example 1 in terms of simplification of the sea-component removal step and waste liquid treatment, and the productivity as ultrafine fibers was extremely good. The results are shown in Table 2.

[0104] [Example 12] A sea-island composite fiber was produced as described in Example 1, except that polypropylene 2 (PP2, melting point: 162°C, melt viscosity: 130 Pa s) was used as the A polymer.

[0105] In this case, the melt viscosity of polymer A was higher than that of polymer B, and the fluidity of polymer B was relatively high, which prevented the bonding of polymer A to itself, and the cross section formability of the produced sea-island composite fibers was extremely good. The results are shown in Table 2.

[0106] [Table 1]

[0107] [Table 2] [Explanation of symbols]

[0108] L: Center-to-center distance between two polymer distribution holes (L AA’ is the center-to-center distance between adjacent polymer A distribution holes with the shortest center-to-center distance, L BB’ is the center-to-center distance between adjacent B polymer distribution holes with the shortest center-to-center distance, L AB is the shortest center-to-center distance between adjacent A polymer and B polymer distribution holes) D: Diameter of polymer distribution hole (D A A is the diameter of the polymer distribution hole, D B (B is the diameter of the polymer distribution hole) 1: Introduction board 2: Distribution plate 3: Publishing 4: Distribution groove 5: Distribution hole 6: Discharge introduction hole 7 : Reduction hole 8: nozzle outlet 9: A polymer distribution hole 9': Adjacent A polymer distribution hole 10: B polymer distribution hole 10': Adjacent B polymer distribution hole 11: B polymer distribution hole present in the sea-island type distribution hole group 12: Polymer B distribution hole located outside the island-type distribution hole group

Claims

1. 1. A composite spinneret which forms an islands-in-sea cross section by joining a polymer A stream and a polymer B stream from distribution holes for distributing each polymer component and then compressing the resulting mixture, wherein the A and B polymer distribution holes in an islands-in-sea type distribution hole group, in which a polymer A distribution hole is surrounded by a plurality of polymer B distribution holes, are drilled so as to satisfy the following formulas (formula 1), (formula 2) and (formula 3), the ratio of the number of polymer B distribution holes present outside the islands-in-sea type distribution hole group to the number of polymer B distribution holes present in the islands-in-sea type distribution hole group is 0.05 or less, the number of polymer A distribution holes present in the islands-in-sea distribution hole group is 100 or more, and the ratio of the distance between the A and B polymer distribution holes (L AB ) to the number of polymer A distribution holes is 2×10 −3 mm / hole or more. L ＢＢ’ / L ＡＡ’ ≦1.0 (Equation 1) L ＡＢ / L ＡＡ’ ≥0.5 (Equation 2) 0.25≦D / L ＡＢ ≤0.70 (Equation 3) Here, L is the center distance between two polymer distribution holes, and L ＡＡ’ is the center-to-center distance between adjacent A polymer distribution holes with the shortest center-to-center distance, L ＢＢ’ is the center-to-center distance between adjacent B polymer distribution holes with the shortest center-to-center distance, L ＡＢ is the shortest center-to-center distance between adjacent polymer A and polymer B distribution holes, and D is the diameter of the polymer distribution holes.

2. A method for producing a sea-island composite fiber, using the composite spinneret of claim 1.

3. The method for producing a sea-island composite fiber according to claim 2, wherein the A polymer is a polyolefin.

4. 4. The method for producing a sea-island composite fiber according to claim 2 or 3, wherein the B polymer is a polyester having a melting point of 230°C or higher, and the island ratio calculated as a weight ratio is 50% to 90%.

Images