JP2005060883A - Melt-spinning method and spinneret pack therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method capable of stably carrying out melt spinning of a fiber having good quality for a long period without generating unevenness of thickness between fibers produced when the fiber having small fineness and profiled section is melt-spun and to provide a spinneret pack therefor and to provide a spinneret pack which can relatively inexpensively and readily be prepared. <P>SOLUTION: The melt-spinning method comprises providing a back pressure-producing member (6) in which a back pressure-producing hole (H1) is bored in accordance with each discharge hole one by one immediately above a spinneret (8) in which a discharge hole (H2) group for spinning a single fiber group having a profile cross section shape is bored to produce the back pressure, supplying a thermoplastic polymer through the back pressure-producing hole (H1) to each of the discharge hole (H2) and spinning the thermoplastic polymer from the discharge hole (H2) group, when carrying out melt spinning of a thermoplastic polymer by using the spinneret pack. The apparatus for carrying out the melt spinning method is also provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for melt spinning synthetic fibers made of a thermoplastic polymer (hereinafter referred to as “polymer”) such as polyester fiber and polyamide fiber, and a spinneret pack for the method. More specifically, the present invention relates to a method for melt-spinning thermoplastic synthetic fiber having a different cross-sectional shape different from a circular shape in the spun fiber and a spinneret pack for the same.

  Conventionally, a fiber having a cross section of a flat cross section, a hollow cross section, a trilobal cross section, a cross-shaped cross section, or the like is a fiber having a circular cross section that has been conventionally produced when used for clothing or industrial materials. It is known that properties and performance that could not be realized can be realized. For example, it has various advantages such that a bulky, light and voluminous fiber material can be obtained, and because of its complicated cross-sectional shape, a large water absorption performance can be obtained between fibers by capillary action.

  Therefore, in order to produce a fiber having such an irregular cross-section by melt spinning, as a discharge hole drilled in the spinneret built in the melt spinneret pack, by combining a slit-shaped hole or a circular-shaped hole, It has been practiced to melt-spin a fiber having a complicated profile as described above. Note that in melt spinning using a spinneret having such discharge holes, the above-mentioned deformed cross-sectional shape is obtained by coalescence of the polymer flow during or immediately after discharge of the polymer to be spun from the discharge holes. Fiber is produced.

  Under such circumstances, in recent years, it has been strongly desired to reduce the thickness of the fiber in order to further improve the above properties and performance as a modified cross-section fiber required in the market. . However, in response to such a request, when a modified cross-section fiber having a fine fineness is to be produced, if the polymer is spun from the discharge hole having the shape and configuration as described above, the fiber thickness spots (fiber Abnormalities such as thick spots in the length direction and thick spots between fibers) and spots in the cross-sectional shape are likely to occur, and there has been a problem that defects when a product such as a woven fabric is manifested. Such a problem also occurred in the conventional discharge hole for spinning the circular cross-section fiber, but when spinning the irregular cross-section fiber, the shape of the discharge hole drilled in the spinneret is complicated. Therefore, the problem becomes more prominent due to the fact that the processing accuracy and the flow state of the polymer in the discharge hole are entangled and the problem becomes more obvious, and the fiber fineness to be spun is further reduced. It has been done.

  For the reasons described above, in the melt spinning process of the modified cross-section fiber with finer fineness, occurrence of fiber thickness unevenness is suppressed, and a high level of cross-sectional shape uniformity is required. In other words, with respect to the thickness unevenness that occurs in the length direction of the fiber, the dead space in which the polymer stays for a long time is present in the spinneret pack, so that the polymer receives an excessive amount over a long period of time. It has been found that deterioration occurs due to thermal history, and the deteriorated polymer is generated by being sent to the discharge holes formed in the spinneret. That is, when the polymer is thermally deteriorated, the molecular weight is reduced to generate viscosity spots, and the discharge pressure when the polymer causing such viscosity spots is discharged from the discharge holes varies to Become. In addition, if a polymer that has undergone thermal degradation is included in a part of the fiber, thinning spots (thickness spots) occur in the process of thinning of the fiber after spinning, and this is a thickness spot in the length direction of the fiber. Connected to.

  Therefore, in order to solve such problems related to dead space, for example, Japanese Patent Laid-Open No. 5-339808 proposes a technique for reducing dead space generated in a distribution plate for distributing a polymer. In this technique, in order to distribute the polymer evenly with substantially the same residence time without allowing the polymer to stay in the spinneret pack for a long time, the introduction hole group that is drilled in the distribution plate to distribute the polymer It has been proposed to distribute the hole diameter and hole length from the center to the outer periphery of the spinneret pack.

  Certainly, by using this conventional technique, the dead space in the spinneret pack can be reduced, and the thickness unevenness in the length direction of the fiber can be reduced. However, with this prior art, it is difficult to suppress the unevenness in the thickness between fibers that occurs when manufacturing the above-mentioned irregular cross-section fibers and fine fibers. This is because even if the dead space in the spinneret pack is eliminated and the generation of deteriorated polymer is suppressed, if the polymer cannot be uniformly fed to the respective discharge holes drilled in the spinneret, This is because the uneven thickness of the fiber generated in the above cannot be eliminated.

  Therefore, as a conventional technique for solving such a problem, for example, Japanese Patent Application Laid-Open No. 2003-113523 proposes that the filter medium installed on the spinneret has a tatami-woven structure. That is, this prior art has a vector perpendicular to the direction of the polymer flow before passing through the filter sent from the upstream side of the spinneret by providing the above-described filter directly above the spinneret. The purpose is to have a flow, thereby reducing the variation in the flow rate of the polymer flowing directly above the spinneret. In other words, this conventional technique is characterized in that the flow direction of the polymer is aligned downward by the rectifying action of the filter installed immediately above the spinneret.

  Certainly, when such a conventional technique is used, the flow direction of the polymer supplied to the spinneret can be rectified in one direction. However, the discharge hole group drilled in the spinneret must be provided at a predetermined interval. For this reason, even if a polymer with the same flow direction is supplied to the spinneret, the polymer supplied to the position where the discharge hole is drilled can maintain the flow direction as it is, but it is supplied to other locations. The polymer made flows into the discharge hole while changing its flow direction immediately above the spinneret. In addition, in this prior art, the spinneret and the filter are in direct contact with each other, and a space is not substantially formed immediately above the spinneret. For this reason, the polymer flow is mixed in the process of flowing into the discharge hole so that the polymer flow rectified by the corner and the filter wraps around the spinneret and cannot be uniformly fed to each discharge hole of the spinneret.

  The prior art described above is intended to eliminate the dead space existing in the spinneret pack or prevent the flow direction and flow velocity of the polymer sent to the spinneret from causing a difference in each discharge hole. is there. However, in addition to these problems, in order to obtain a modified cross-section fiber, if the discharge hole becomes a complicated shape, the polymer flow path of the discharge hole also becomes complicated, and the flow rate distribution of the polymer when passing through this flow path And pressure loss slightly change. In addition to this, in order to produce fine fibers, if the shape of the discharge hole needs to be reduced accordingly, it is necessary to process the discharge hole into a precise shape. Limits arise. Nevertheless, when trying to drill high-precision discharge holes in the spinneret, it is required to process a large number of discharge hole groups into a single spinneret with high accuracy and no variation. Combined with a state in which failure is not allowed, an enormous amount of time is required for processing, and the processing yield is extremely reduced. Then, enormous processing costs and processing time are required for producing the spinneret.

  In addition, in the conventional technology, in addition to the techniques described above, in order to make the amount of polymer spun from each discharge hole uniform, the discharge pressure acting on the discharge hole group formed in the spinneret is made uniform. There have been attempts to do so. In this prior art, when the discharge hole shape itself is a dimension, for example, when the discharge hole shape is a slit hole or a circular hole, the width of the slit hole is reduced or the diameter of the circular hole is reduced. Or by increasing the length of the discharge hole in the polymer flow direction (capillary length), the back pressure acting on each discharge hole is increased. The reason for this is that by increasing the back pressure in this way, the ratio of the pressure loss that occurs when the polymer flows through each discharge hole to the discharge pressure is reduced compared to the back pressure, and the processing accuracy of each discharge hole is reduced. This is because fluctuations in pressure loss caused by variations in the pressure can be reduced, and variations in discharge pressure can be reduced.

However, in this prior art, as described above, when manufacturing a fiber having an irregular cross-sectional shape, it is difficult to change the shape of the discharge hole in order to obtain the required fiber cross-sectional shape, and the discharge is inevitably performed. There is a problem that the hole shape is determined to be a fixed shape. Therefore, it is essentially difficult to reduce the width of the slit holes and the diameter of the circular holes. In this case, in order to equalize the polymer pressure in each discharge hole, it is necessary to increase the capillary length. Will respond. However, the discharge hole drilled in the spinneret for melt-spinning a fiber having a fineness and an irregular cross section needs to have a relatively small shape in accordance with the fineness, and the capillary length is increased. It is more difficult to perforate the discharge hole having the irregular cross section in the spinneret than to process the discharge hole having a short capillary length. Therefore, such conventional technology has a worse processing yield than the drilling of fine fineness discharge holes with ordinary capillary lengths, which increases the processing cost and processing time. In addition, depending on the capillary length, it becomes impossible to process a predetermined irregular section discharge hole.
JP-A-5-339808 Japanese Patent Laid-Open No. 2003-113523

  The present invention has been made for the purpose of solving the problems of the prior art described above. That is, the present invention is capable of stably melting high-quality fibers over a long period of time without generating unevenness in the thickness between fibers, which occurs when melt-spinning fibers having a small cross section and an irregular cross-section. It is an object of the present invention to provide a spinneret pack which can be spun and a spinneret pack therefor, and which can be manufactured relatively inexpensively and easily.

  The present inventor is particularly suitable for melt-spinning thermoplastic synthetic fibers such as polyester fibers and polyamide fibers, whose cross-sections have irregular cross-sections such as flat cross-sections, hollow cross-sections, tri-loval cross-sections, and cross-leaf cross-sections. While researching the melt spinneret pack, the present inventors reached the present invention in the process of finding out various problems as described in the “Background Technology” column and intensively studying to solve these problems.

  In other words, in order to uniformly discharge the polymer from each of the discharge holes formed in the spinneret, the flow direction of the polymer supplied to each discharge hole is simply aligned, or the dead space generated in the spinneret pack is eliminated. It has been found that this cannot be achieved simply by doing. In particular, it has been found that the situation is further deteriorated for a spinneret pack suitable for spinning a fiber having a shape of each discharge hole smaller than that of a normal one and a fiber having an irregular cross section.

  Finally, the discharge pressure acting on each of the discharge holes drilled in the spinneret can be surely made uniform, and the processing accuracy of the discharge holes must be processed with the highest precision. As a result, the inventors have paid attention to the fact that the above-mentioned problems can be solved as long as they are processed to a certain level of accuracy. However, in spite of the above-mentioned attention of the present inventor, it is extremely difficult to realize this, and the pressure loss that the polymer passing through each discharge hole receives in each discharge hole contributes to the processing accuracy of each discharge hole. A spinneret pack that can be controlled so that the discharge pressure does not change greatly was examined by trial and error. In the process, the present invention was completed for the first time when the idea described below could be achieved by adopting the means described below.

  Here, as an invention relating to the melt spinning method according to claim 1, “in the method of melt spinning a thermoplastic polymer, each directly above a discharge hole group for spinning a single fiber group having an irregular cross-sectional shape” A back pressure generating hole is provided in a one-to-one correspondence with the discharge hole to generate a back pressure, and the thermoplastic polymer is supplied to each of the discharge holes through the back pressure generating hole, from the discharge hole group. There is provided a melt spinning method characterized in that the thermoplastic polymer is spun.

  At that time, as in the invention described in claim 2, “the pressure loss of the thermoplastic polymer passing through the discharge hole is P1 (MPa), and the pressure loss of the thermoplastic polymer passing through the back pressure generation hole is set. The melt spinning method according to claim 1, wherein melt spinning is performed under a condition that P1 and P2 satisfy a relational expression of 0.5 ≦ P1 / P2 ≦ 30 when It is preferable to do.

  Further, as in the third aspect of the invention, the pressure loss of the thermoplastic polymer passing through the discharge hole is defined as P1 (MPa), and the pressure loss of the thermoplastic polymer passing through the back pressure generating hole is defined as The melt spinning method according to claim 1 or 2, wherein when P2 (MPa), these P1 and P2 perform melt spinning under conditions satisfying a relational expression of 3 ≦ P1 + P2 ≦ 30 ”. preferable.

  Furthermore, as in the invention according to claim 4, the melt spinning according to any one of claims 1 to 3, wherein the fineness of the single fibers constituting the single fiber group is 0.1 to 4.0 dtex. The “method” is preferred.

  Next, as an invention relating to the melt spinneret pack according to claim 5, “the spinneret pack for melt spinning the thermoplastic polymer is a discharge hole for spinning out a single fiber group having an irregular cross-sectional shape. Back pressure generation having a spinneret in which a group is drilled and a back pressure generating hole group that is installed in close contact with the spinneret and is drilled corresponding to each of the discharge hole groups on a one-to-one basis A melt spinneret pack comprising a member.

  At that time, as in the invention described in claim 6, it is preferable to use the “melt spinneret pack according to claim 5 in which a reduced flow path is formed in the back pressure generating hole”.

  Further, as in the invention according to claim 7, "the thermoplastic polymer at the time of passing through the discharge holes provided in one-to-one correspondence with the back pressure generation holes and the back pressure generation holes, respectively. When the pressure loss is P1 (MPa) and P2 (MPa), respectively, the shape of the back pressure generating hole is determined so that P1 and P2 satisfy the relational expression of 0.5 ≦ P1 / P2 ≦ 10. Preferably, the melt spinneret pack according to claim 5 or 6 is used.

  Further, as in the invention described in claim 8, “a step is not provided in a connecting portion between a polymer outlet portion of the back pressure generation hole and a polymer inlet portion to the discharge hole. The melt spinneret pack according to any one of 7 is preferable.

  And, as in the invention according to claim 9, "the melt according to any one of claims 5 to 8, wherein the back pressure generating hole is formed outside a circular region having a diameter of at least 10 mm from the center of the spinneret. A spinneret pack is preferable.

  According to the present invention described above, particularly when a specially shaped cross-section fiber having a fineness is melt-spun, it is refined in accordance with the fineness of a single fiber group that spouts discharge holes having a modified cross-section formed in a spinneret. Even if it has to be, there is no need to improve the processing accuracy of the discharge holes, and there is an effect that fibers having a small thickness unevenness and good quality can be stably manufactured over a long period of time.

  The embodiment of the present invention described above will be described in detail together with the operation thereof with reference to the drawings.

  FIG. 1 is a schematic component configuration diagram schematically illustrating a spinneret pack for melt spinning thermoplastic synthetic fibers such as polyester fibers and polyamide fibers of the present invention. Usually, the spinneret pack is heated to a predetermined temperature in a pack dome of a spin block (not shown) on which the spinneret pack is mounted. Accordingly, as is well known, a heating device (not shown) for heating the spinneret pack is incorporated in the spin block, and a melt extruder (see FIG. (Not shown) or the like is provided. At this time, it is well known that this is also supplied to the spinneret pack while being continuously measured by a constant supply device (not shown) such as a gear pump normally incorporated in the spin block.

  The spinneret pack of the present invention is not particularly limited to the example shown in FIG. 1 as long as it satisfies the gist of the present invention, and it goes without saying that the spinneret pack can also be applied to a known spinneret pack. Yes. For example, the embodiment of the melt spinneret pack of FIG. 1 is for spinning a fiber made of one kind of polymer, and this is applied to a melt spinneret pack of a composite fiber made of two or more polymers. It can also be applied to a mixed spinneret pack in which one polymer is mixed with another polymer. In addition, a multi-eye spinneret capable of spinning a multi-spindle thread (for example, a double-spindle thread or a 4-spindle thread) in which a single spinneret pack has a large number of bases incorporated therein. It can also be applied to packs. Further, the structure for preventing the polymer leakage from the spinneret pack can be applied to the “forced sealing method” exemplified in FIG. 1 and the other so-called “self-sealing method”. Yes. As is well known, the “self-sealing method” in the present invention is to prevent polymer leakage by utilizing the pressure of the polymer introduced into the spinneret pack.

  Here, first, the reference numerals described in FIG. 1 will be described. 1 is a spinneret pack and 2 is a main body member. As shown in the figure, the main body member 2 is divided into an upper member 2a, an intermediate member 2b, and a lower member 2c. The upper member 2a and the intermediate member 2b are interposed via a seal member 3 such as a gasket. Although not shown, it is tightened at a position indicated by a one-dot chain line by a fastening member such as a hexagon socket head bolt. Similarly, the lower member 2c and the intermediate member 2b are also indicated by a dashed line by a fastening member (not shown) through a filter 7 with a rim having a sealing material such as an aluminum rim on the outer edge of the filtration medium (filter). It can be tightened with. In this manner, in the well-known forced-seal type spinneret pack 1 illustrated in FIG. 1, the polymer introduced into the inside is sealed by the seal member 3 so as not to leak to the outside.

  Further, a filter member 4 and a bridge plate 5 that supports the filter member 4 are provided inside the main body portion 2 that is sealed so as not to leak the polymer. The filter member 4 removes foreign matters in the polymer. In addition, the amount of polymer retained in the pack is also controlled. In addition, although the said filter member 4 can use a metal sand, the porous material similar to this, etc. suitably, not only these but other well-known filter media can be used. However, in the case where the filter member 4 is constituted by a granular filter medium 4a such as metal sand as shown in the figure, a filter 4b is installed to prevent this from flowing out downstream of the filter medium 4a.

  However, the filter 7 normally serves to collect foreign substances in the molten polymer that could not be collected by the filter 4b. Therefore, it is preferable to use a filter having a smaller opening than the filter 4b. As a suitable filtration medium (filter), a porous material such as metal fiber woven fabric, non-woven fabric, and sintered metal can be appropriately selected and used. Further, the filter 7 can be a filter in which the outer peripheral part of the molten polymer passage part is reinforced with a metal rim, or a filter without a rim and a combination of a sealing material (not shown) on the outer peripheral part. In view of the ease of assembling the pack, it is preferable to use the filter 7 with rim described above.

  Next, the member illustrated by reference numeral 6 in FIG. 1 is a “back pressure generating member” which is one of the main features of the melt spinning nozzle pack of the present invention. Is provided. As described above, the back pressure generating member 6 plays an extremely important role when spinning a fiber having an irregular cross section with a small fineness from the spinneret 8 having a large number of discharge hole groups. This point will be described in detail below.

  The back pressure generating member 6 according to the present invention is provided with a back pressure generating hole H1 formed in a one-to-one correspondence directly above the position where the discharge hole H2 formed in the base 8 is formed. It is characterized by. That is, by adopting such a configuration, it is possible to individually set a predetermined back pressure for each of the discharge holes H2 formed in the base 8. This is because the absolute value of the back pressure applied to each discharge hole H2 can be substantially set by the hole diameter and the hole length of the throttle hole H1a of the back pressure generation hole H1.

  That is, in order to explain this more specifically, in order for a polymer with a constant flow rate to be supplied to each discharge hole H2, it must be sure to pass through the back pressure generation hole H1. When a polymer having a constant flow rate passes through the back pressure generation hole H1, assuming that the polymer follows the Hagen-Poiseuille equation, the magnitude of the pressure loss is inversely proportional to the fourth power of the diameter of the throttle hole H1a. And is proportional to the first power of the hole length. Therefore, by increasing the processing accuracy of the hole diameter and the hole length of the throttle hole H1a, a desired back pressure can be applied to each discharge hole on a one-to-one basis. In addition, the hole diameter and the hole length of the polymer introduction hole H1b of the back pressure generation hole H1 should be sufficiently larger than the hole diameter of the throttle hole H1a, and the processing accuracy is much less than that of the throttle hole H1a. I don't need it. In addition, since the hole shape of the throttle hole H1a may be a round cross-sectional hole, it does not require difficult processing unlike the irregular cross-sectional hole, so that the processing cost is reduced and the processing period is shortened. However, it goes without saying that the processing accuracy can be remarkably improved.

  On the other hand, the discharge hole H2 formed in the base 8 no longer has to play the role of generating a back pressure for reducing fluctuations in the discharge pressure for discharging the polymer as in the prior art. For this reason, it becomes possible to further shorten the hole length (capillary length) of each discharge hole H2, and it is easier to process the discharge hole H2 having a complicated and smaller irregular cross-sectional shape as compared with the case where the capillary length is long. This is more convenient in processing the discharge hole H2 with high accuracy. In addition, when the capillary length of the modified cross-sectional hole H2a2 portion is shortened, the pressure loss of the polymer passing through this portion becomes smaller, and the influence on the discharge pressure of the polymer discharged from the discharge hole H2 is reduced accordingly.

  In addition, in this example, since the contact surface of the spinneret 8 and the back pressure generating member 6 is processed sufficiently smoothly and with good flatness in this example, they are joined to each other by metal touch. However, the molten polymer supplied from the back pressure applying hole H1 does not leak from the contact surface between the spinneret 8 and the back pressure generating member 6. At this time, if necessary, a sealing material such as a gasket may be provided on the contact surface.

  For the reasons described above, in the base 8 constituting the spinneret pack of the present invention, the capillary length H2a can be further shortened compared to the conventional one, so that the shape of the discharge hole H2 can be processed with higher accuracy. On the other hand, even if variations occur within a range within the processing accuracy of the shape of the discharge hole H2 (particularly, the shape of the modified cross-sectional hole H2a), a high back pressure is already generated by the action of the back pressure generating member 6 for each discharge hole H2. Therefore, the influence of machining accuracy is reduced. In this way, the molten polymer that has passed through the rim-attached filter 7 installed immediately above the back pressure generating member 6 is supplied to the back pressure generating hole H1 perforated in the back pressure generating member 6, and the flow path diameter decreases. A large back pressure (pressure loss) is generated on a one-to-one basis for each discharge hole H2 by the action of the throttle hole H1a. Since the back pressure (pressure loss) generated at this time can be sufficiently larger than the pressure loss generated in the discharge hole H2, the processing accuracy of each discharge hole H2 varies, resulting in this variation. Even if the pressure fluctuation occurs, it can be reduced to such an extent that the influence can be absorbed.

  Hereinafter, the characteristics of the present invention described so far will be specifically described using numerical values. In the melt spinning method of the present invention, the pressure loss of the polymer passing through the back pressure generation hole H1 is defined as P1 (MPa). When the pressure loss of the polymer passing through the discharge hole H2 is P2 (MPa), melt spinning is performed under the condition that these P1 and P2 satisfy the relational expression of 0.5 ≦ P1 / P2 ≦ 10 It is preferable. Note that, under the condition of P1 / P2 <0.5, when variation occurs in the hole shape to be processed by the discharge hole H2 due to the processing accuracy, in order to suppress the influence of pressure fluctuation caused by the variation, The effect of installing the pressure generating member 6 cannot be expected so much, and the discharge amount unevenness of the polymer cannot be suppressed. In addition, when P1 / P2> 10, particularly when a thin fiber having a small fineness is spun, the shape of the discharge hole H2 is relatively reduced as compared with the normal case, and the pressure loss (P2) at the discharge hole H2 is reduced. ) Is increased, and the pressure loss (P1) of the polymer passing through the back pressure generation hole H1 becomes larger, which causes a problem in the pressure resistance of the spinneret pack and easily causes polymer leakage. It is not preferable.

  Moreover, when P1 + P2 is less than 3 MPa, the overall pressure loss is low, and even if the back pressure generating member 6 is added, the dispersibility of the molten polymer is deteriorated. If P1 + P2 exceeds 30 MPa, the time until the pressure in the spinneret pack 1 gradually increases and reaches the pressure resistance value due to the influence of foreign matter trapped in the filter 7 or the like is shortened, and the spinneret pack 1 It is necessary to exchange frequently, which is not preferable because the productivity deteriorates. In other words, the pressure in the spinneret pack 1 gradually increases with the start of spinning due to factors such as clogging of the filter due to foreign matter generally captured by the filter 7 and the like, so the initial pressure needs to be reduced as much as possible. is there.

  In the spinneret pack of the present invention described above, the polymer that finally passes through the discharge hole H2 is spun from the spinneret 8 to be fiberized. At this time, the thickness unevenness in the length direction of the fiber is greatly influenced by the cooling process for cooling the spun fiber. Therefore, the cooling air can be uniformly blown to the single fiber group spun from the discharge hole H2 group, and further, the base 8 can be passed between the spun single fiber groups. It is important to determine the arrangement of the discharge hole H2 group to be drilled in.

  The spinneret pack of the present invention can be suitably used for melt-spinning a fiber having a modified cross section. Regarding the cross-sectional shape of the discharge hole H2 important for spinning the modified cross-section fiber (including hollow fibers). There is no particular need to limit this, and well-known ones can be used. However, it goes without saying that the effect of using the spinneret pack of the present invention is greater as the discharge holes require complicated and precise processing as already described. In addition, if the example is enumerated, the thing of the shape illustrated in FIG. 2 can be used. For example, a discharge hole formed by combining slit-shaped flow paths as shown in FIG. 2A, or a discharge hole formed by combining a slit-shaped flow path and a circular flow path as shown in FIGS. 2B to 2C. Furthermore, the discharge hole etc. which are comprised from several independent slit-shaped flow paths like FIG.2 (d)-FIG.2 (e) can be illustrated.

  As described above, the present invention has a great effect by using the back pressure generating member 6. However, as illustrated in FIG. 1, the filter 7 is provided immediately above the back pressure generating member 6. In such a case, it is preferable to pay attention to the arrangement of the back pressure generation holes H1. Therefore, this point will be described with reference to FIG. 3 in which the back pressure generating member 6 is exemplified by a schematic plan view. As shown in FIG. 3, in the spinneret pack of the present invention, the molten polymer is supplied from the upper body member 2 a of the spinneret pack to the center of the back pressure generating member 6. It is desirable not to install the back pressure generation hole H1 in the region A within a diameter of 10 mm from the center near the center. This is because the molten polymer supplied from the pack upper body 2 to the center of the back pressure generating member 6 is distributed and supplied to the back pressure generating hole group along the filter 7 installed immediately above the back pressure generating member 6. This is because, in the central portion of the back pressure generating member 6, the flow of the molten polymer becomes faster than the peripheral portion and is affected by the dynamic pressure. For this reason, even if the filter 7 serves as a cushion, the influence cannot be completely removed, and the discharge amount of the molten polymer in the center portion increases. In particular, as P1 / P2 approaches 0.5, which is the allowable lower limit, the effect of providing the back pressure generating member 6 decreases, so this influence cannot be ignored. Therefore, when it is desired to further increase the uniformity of the polymer discharge from the discharge hole H2, it is preferable to drill the back pressure generation hole H1 outside the region A that is affected.

  Next, it goes without saying that, in order to melt-spin fibers of good quality without thick spots over a long period of time, it is preferable to eliminate dead space and prevent abnormal polymer retention. This is no exception in the relationship between the back pressure generating member 6 and the base 8 of the present invention. Therefore, it is preferable not to provide a step with an abrupt change in the flow path area at the connection portion formed between the polymer outlet portion of the back pressure generation hole H1 and the polymer inlet portion to the discharge hole H2. Therefore, as shown in FIG. 4, an enlarged flow passage H1c whose flow passage area gradually increases is provided at the polymer outlet of the back pressure generation hole H1, and the polymer flows smoothly into the polymer inlet to the discharge hole H2. It is preferable to make it.

  That is, by eliminating the step in this way, it is possible to reduce dead space that causes the polymer to stay for a long time, and to suppress deterioration of the polymer. If it does so, the polymer which deteriorated will not mix in a fiber, and the fault of a product can be suppressed. The enlarged portion H1c may be formed with a gently curved surface other than the tapered shape as shown in FIG. 4, and the important thing is to prevent the step from being substantially formed. As long as it can be achieved, there is no particular limitation on its shape.

  According to the melt spinning method and the apparatus therefor according to the present invention, when a synthetic fiber having a modified cross section made of a thermoplastic polymer is melt-spun, the quality free from thickness spots (fineness spots) along the length of the fiber. Can be obtained more stably, and can be suitably used as the fineness of the single fiber to be melt-spun becomes smaller.

  In addition, even if there is some variation in the processing accuracy of the discharge holes with irregular cross-sections drilled in the spinneret, a melt spinneret pack that does not cause quality variations between individual fibers can be manufactured inexpensively and easily in a short period of time. can do.

The front sectional view which illustrated typically the schematic structure of the melt spinneret pack of the present invention is shown. The plane sectional view which illustrated various discharge hole shapes of the spinneret used for the melt spinneret pack of the present invention is shown. The top view which illustrated the back pressure generation member used for the melt spinneret pack of the present invention is shown. The front sectional view which illustrated typically the schematic structure of other embodiments concerning the melt spinneret pack of the present invention is shown.

Explanation of symbols

1 Melt Spinneret Pack 2 Body Member 2a Upper Body Member 2b Middle Body Member 2c Lower Body Member 3 Seal Member 4 Filter Member 4a Granular Filter Material 4b Filter Part Filter 5 Bridge Plate 6 Back Pressure Generating Member 7 Rim Filter 8 Spinneret H1 Back pressure generation hole H1a Restriction hole H1b Introduction hole H2 Discharge hole H2a Modified cross-sectional hole H2b Introduction hole

Claims (9)

  In the method of melt spinning a thermoplastic polymer, a back pressure generating hole is provided in a one-to-one correspondence with each discharge hole immediately above the discharge hole group for spinning a single fiber group having an irregular cross-sectional shape. , Supplying the thermoplastic polymer to each of the discharge holes through the back pressure generation hole, and spinning the thermoplastic polymer from the discharge hole group.   When the pressure loss of the thermoplastic polymer passing through the back pressure generation hole is P1 (MPa) and the pressure loss of the thermoplastic polymer passing through the discharge hole is P2 (MPa), these P1 and P2 The melt spinning method according to claim 1, wherein melt spinning is performed under conditions satisfying a relational expression of 0.5 ≦ P1 / P2 ≦ 10.   When the pressure loss of the thermoplastic polymer passing through the back pressure generation hole is P1 (MPa) and the pressure loss of the thermoplastic polymer passing through the discharge hole is P2 (MPa), these P1 and P2 The melt spinning method according to claim 1 or 2, wherein the melt spinning is performed under conditions satisfying a relational expression of 3≤P1 + P2≤30.   The melt spinning method according to any one of claims 1 to 3, wherein the single fiber constituting the single fiber group has a fineness of 0.1 to 4.0 dtex.   A spinneret pack for melt-spinning a thermoplastic polymer is in close contact with a spinneret in which a discharge hole group for spinning a single fiber group having an irregular cross-sectional shape is formed, and directly above the spinneret. A melt spinneret pack comprising: a back pressure generating member having a back pressure generating hole group that is installed and formed in one-to-one correspondence with each of the discharge hole groups.   The melt spinneret pack according to claim 5, wherein a reduced flow path is formed in the back pressure generation hole.   When the pressure loss of the thermoplastic polymer at the time of passing through the back pressure generation hole and the discharge hole provided corresponding to the back pressure generation hole is P1 (MPa) and P2 (MPa), respectively, The melt spinneret pack according to claim 5 or 6, wherein the shape of the back pressure generating hole is determined so that P1 and P2 satisfy a relational expression of 0.5≤P1 / P2≤10. .   The melt spinneret pack according to any one of claims 5 to 7, wherein a step is not provided at a connection portion between the polymer outlet portion of the back pressure generation hole and the polymer inlet portion to the discharge hole.   The melt spinneret pack according to any one of claims 5 to 8, wherein the back pressure generating hole is formed outside a circular region having a diameter of at least 10 mm from the center of the spinneret.

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