JP2006214033A - Spinneret for melt blend spinning and method for producing ultrafine fiber using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spinneret for melt blend spinning uniformly elongating an island component in the fiber axis direction and stably affording a melt blend spun fiber having the island component at a high aspect ratio in the melt blend spinning of polymers in which an incompatible additive is kneaded. <P>SOLUTION: A blended resin passing through and flowing the interior of a spinneret is subjected to a flow field in which an elongational flow field is moderately combined with a shear flow field. Thereby, the shape and oriented state of the island phase are controlled. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a spinneret. More particularly, the present invention relates to a mixed spinning die used for incompatible mixed spinning and a method for producing ultrafine fibers using the same.

  In recent years, various methods have been devised for spinning a combination of a plurality of component polymers in order to give the fiber various functions. Examples thereof include incompatible mixed spinning and composite spinning (for example, Patent Documents 1 and 2). Among these, incompatible mixed spinning is a method in which a plurality of components of polymers and resins that are incompatible with each other are mixed in advance, and the mixed resin is spun in the same manner as ordinary single component spinning. In the case of incompatible spinning, the mixed state of the components viewed from the cross section of the fiber forms a sea-island structure. By removing the island component by removal, an ultrafine fiber or nonwoven fabric having a fiber diameter of 1 μm or less can be easily obtained. There are various determinants such as the mixed composition of the mixed resin, melt viscosity, compatibility, and mechanical mixing conditions in the formation of the structure of the sea-island phase. By controlling and adjusting these factors, the desired predetermined structure can be obtained. Can be formed.

  The ultrafine fibers produced in this way are used as a base material for artificial leather, a filler for resin reinforcement, and the like (see, for example, Patent Document 3), and other applications are expected.

  In addition, because it is possible to develop a unique function as the fiber diameter becomes thinner, a technique to stretch the island component more is desired, but the production of sea-island type mixed spun fibers with a higher softening point of the island component than the sea component In the process, even if you try to stretch the island component by stretching the formed yarn, it is difficult to deform because the island component is solidified first, and only the sea component will be stretched, and the aspect ratio of the island phase There was a problem that it was difficult to control.

  On the other hand, it is said that the response of the polymer chain to the flow field is essentially different between the shear flow field and the extension flow field with respect to the influence that the polymer melt such as resin is transported. Is said to cause the rotation of the molecule, whereas the elongated flow field causes the chain molecule to be stretched. Therefore, attention can be paid to the structure of the spinneret as a technique for controlling the island component. It is known that the state of the island component in the mixed spun fiber is greatly influenced by passing through the spinneret, and examples include a technique for finely dispersing and dispersing the additive component by controlling the shearing method (for example, (See Patent Document 4).

  In particular, in the production process of sea-island type mixed spun fiber, where the island component has a higher softening point than the sea component as described above, it is difficult to stretch the island component that tends to solidify after yarn formation. As a technique for stretching the island component when passing through the spinneret to achieve a high aspect ratio, a spinneret structure capable of efficiently providing an extension flow field is desired.

JP-A-6-158431 JP-A-8-296123 JP-A-5-156579 JP 2003-193322 A

The object of the present invention is to solve the above-mentioned problems of the prior art, and stably obtain a mixed spun fiber having island components with a high aspect ratio by uniformly stretching the island components in the fiber axis direction. It is to provide a base for mixed spinning.
Still another object of the present invention is to provide a method for producing ultrafine fibers using the above mixed spinning base.

  As a result of intensive studies in view of the above-described conventional techniques, the present inventors have made the island phase by making the flow field appropriately combining the extension flow field and the shear flow field with respect to the mixed resin flowing through the spinneret. The present inventors have found that the shape and orientation state can be controlled, and have completed the present invention.

That is, the purpose of the present invention is to
A spinneret used for producing a sea-island type mixed spun fiber from a resin composition, which is an introduction hole, a drawn part and a capillary for introducing a resin composition for forming a sea-island type mixed spun fiber in this order. This is achieved by a mixed spinning die, which is provided with a flow path that is combined and continuously reduced in diameter in the resin discharge direction.

  In the above invention, the angle α formed between the hole wall surface and the central axis in the introduction hole portion that continuously decreases in diameter is 0 ° to 30 °, and in the throttle portion that is the connection portion between the introduction hole portion and the capillary, The angle β formed between the wall surface of the throttle part and the central axis is 10 to 60 degrees, and the Lc / Dc (capillary length / capillary diameter) of the capillary is 0.1 to 10, each of the introduction hole and the throttle part Are included in which the angles α and β are continuously reduced in the resin discharge direction.

Another object of the present invention is to
A method for producing a sea-island mixed spun fiber having a sea component and an island component, and removing the sea component from the sea-island mixed spun fiber to obtain the island component as an ultrafine fiber, having a softening point of 50 ° C to 350 ° C Pitch, polyacrylonitrile, polycarbodiimide, polyimide having a softening point of 50 ° C. to 200 ° C. higher than the softening point of the sea component. , Adding at least one thermoplastic carbon precursor selected from the group consisting of polybenzoazole and aramids as an island component in a volume fraction (Vf) in the range of 0.5% to 150%, then melt-kneading and introducing A combination of holes, constrictions, and capillaries in this order is discharged and solidified from a die having a flow path continuously reduced in diameter in the resin discharge direction to obtain a sea-island mixed spun fiber. The removal of the sea component of 該海 islands mixed spun fibers island component obtained as ultrafine fibers is achieved by the method for producing the ultrafine fiber.

  In the above invention, the angle α formed between the hole wall surface and the central axis in the introduction hole portion that continuously decreases in diameter is 0 ° to 30 °, and in the throttle portion that is the connection portion between the introduction hole portion and the capillary, The angle β formed between the wall surface of the throttle part and the central axis is 10 to 60 degrees, and the Lc / Dc (capillary length / capillary diameter) of the capillary is 0.1 to 10, each of the introduction hole and the throttle part The angles α and β are continuously reduced in the resin discharge direction, the sea component is removed by subjecting the island component to a firing process under the condition of maintaining the shape, and the sea component is removed. The component is made by contacting with a solution having the ability to dissolve the sea component under the condition of maintaining the shape, and the aspect ratio of the island component in the mixed spun fiber (= island phase fiber length (l) / island phase fiber diameter (d)) Is greater than 1 and less than 1 million. Riechiren, poly-4-methylpentene-1 and / or its copolymers, are also included.

  According to the mixed spinning base of the present invention, the additive component inside the mixed spinning fiber can be effectively stretched. In addition, since the fiber surface remains in good condition even during long-term continuous spinning, it is possible to extend the cleaning period (face cleaning period) of the die surface, which can significantly improve productivity. is there.

Hereinafter, the present invention will be described in detail.
The mixed spinning nozzle of the present invention is a spinning nozzle used for producing a sea-island type mixed spinning fiber from a resin composition, and is introduced for introducing a resin composition for forming a sea-island type mixed spinning fiber. It is characterized by comprising a flow path that is combined in the order of a hole, a constriction, and a capillary, and is continuously reduced in diameter in the resin discharge direction, and between the hole wall surface and the central axis in the introduction hole that is continuously reduced in diameter. The angle α formed between the throttle wall and the central axis is 10 ° to 60 °, and the capillary Lc is 0 ° to 30 °. It is preferable that / Dc (capillary length / capillary diameter) is 0.1 to 10, and the angles α and β of the introduction hole and the narrowed portion are continuously reduced toward the resin discharge direction.

Here, the spinneret of the present invention will be described with reference to the drawings describing preferred embodiments.
The spinneret 1 according to the present invention includes a flow path including an introduction hole 2, a throttle portion 3, and a capillary 4 as shown in the schematic diagram of FIG. 1.

  As shown in the schematic diagram of FIG. 3, the conventionally used spinneret has a cylindrical shape in which the introduction hole 2 does not change the cross-sectional area of the flow path. In the present invention, the diameter is continuously reduced in the resin discharge direction. It is characterized by doing. Further, the spinneret that is conventionally used in the narrowed portion 3 also has a constant angle formed between the wall surface and the central axis as shown in the schematic diagram of FIG. 3, but in the present invention, the schematic of FIG. As shown in the figure, the angle is continuously reduced in the resin discharge direction. The locations where the diameter is continuously reduced in the discharge direction may be the introduction hole 2 and the throttle portion 3 or may be combined.

  The melt-kneaded mixed resin flows into the introduction hole 2 from the resin inflow surface 6 of the spinneret 1, is squeezed by the constriction part 3, passes through the capillary (pore) 4, and is discharged from the resin discharge surface 7 to the discharge hole 5. It is discharged through, cooled and solidified, and taken up as a yarn.

  In the introduction hole portion 2 whose diameter is reduced, it is preferable that the angle α formed between the wall surface and the central axis is 0 to 30 degrees, and that the angle continuously decreases toward the resin discharge direction. It is desirable as a structure that gives an elongation flow to the resin. When the angle α is within 30 degrees, the polymer does not shrink rapidly, so that the shear flow does not become more dominant than the extension flow, and the effect is increased. Here, in the case of FIG. 2 and FIG. 3 in which the angle formed between the wall surface and the central axis does not gradually change, α is 0 degree. Moreover, in order to raise | generate an elongate flow efficiently, it is preferable that the flow-path surface in this introduction hole 2 is mirror surface finish.

  In addition, in the narrowed portion 3 which is a connection point between the introduction hole 2 and the capillary 4, the angle β formed between the wall surface and the central axis is preferably 10 degrees to 60 degrees, and more preferably 15 degrees to 30 degrees. is there.

  Exceeding this angle is not preferable because the periphery of the narrowed portion 3 becomes a dead space and polymer retention occurs, resulting in quality problems such as polymer alteration and thermal degradation. Below this angle, nozzle processing becomes difficult, and the die cost increases, which is not preferable.

Furthermore, Lc / Dc (= capillary length / capillary diameter) of the capillary 4 is preferably 0.1 to 10, and more preferably 0.5 to 6.
Below this value, the pressure loss is small and the discharge pressure becomes small. Therefore, when the spinneret has a plurality of discharge holes, the amount of polymer introduced into the introduction hole near the outer periphery of the spinneret 1 is small and large in the center of the base. This is not preferable because the amount of polymer discharged between the discharge holes tends to vary. If Lc / Dc exceeds this value, the discharge pressure when passing through the spinneret 1 is increased, which causes production problems such as quantitativeness of the metering pump and pressure resistance of the apparatus, which is not preferable.

Next, the manufacturing method of the ultrafine fiber of this invention is demonstrated.
The production method of the present invention is a method of producing a sea-island type mixed spinning fiber having a sea component and an island component, and removing the sea component from the sea-island type mixed spinning fiber to obtain the island component as ultrafine fibers,
A pitch having a softening point of 50 ° C to 200 ° C higher than the softening point of the sea component, using a thermoplastic resin having a softening point of 50 ° C to 350 ° C as the sea component, which is incompatible with the sea component. And at least one thermoplastic carbon precursor selected from the group consisting of polyacrylonitrile, polycarbodiimide, polyimide, polybenzoazole, and aramids as an island component in a volume fraction (Vf) of 0.5% to 150%. After the addition, melt-kneading, combined with the introduction hole portion, the narrowing portion and the capillary in this order, discharged from a die having a flow path continuously reduced in the resin discharge direction, solidified to obtain a sea-island type mixed spinning fiber Then, the sea-island type mixed spun fiber is removed from the sea component to obtain the island component as ultrafine fiber.

  At this time, when the volume fraction (Vf) is less than 0.5%, when the sea component is finally removed and only the island component is obtained as a product, the yield is low, whereas it exceeds 150%. Then, the existence ratio of the island phase in the mixed spun fiber becomes too high, and it becomes difficult to finely disperse the island component in the sea component.

  On the other hand, it is said that the response of the polymer chain to the flow field is essentially different between the shear flow field and the extension flow field. It is said that the molecules are stretched. Therefore, the island component can be controlled when the spinneret passes by appropriately combining the shear flow and the extension flow. That is, it is effective to provide a shear flow field when it is desired to align the orientation of the island component, and to apply an extension flow field when the island component is desired to be elongated.

  The mixed spun fiber thus obtained takes a mixed form of sea-island structure as shown in the schematic diagram of FIG. One of the parameters characterizing the form of island phase fibers is the aspect ratio (island phase fiber axial length (l) / island phase fiber cross-sectional direction diameter (d)), but the aspect ratio of island phase fibers is greater than 1. It is less than 1 million, and the island phase fiber diameter (d) is 0.001 μm to 2 μm, preferably 0.001 μm to 1 μm. This is preferable.

  The mixed spinning fiber diameter (D) is preferably 0.5 μm to 200 μm. If the diameter is less than this value, the strength of the yarn is lowered, so that yarn breakage is likely to occur in a winding process or the like, and productivity is deteriorated. Exceeding this diameter is not preferable because when the sea component of the mixed spun fiber is melted and removed with a solvent or the like, it takes time and labor, and the productivity deteriorates.

  Further, as the sea component, at least one thermoplastic resin of polyethylene, poly-4-methylpentene-1 or a copolymer thereof is used, and as the island component, pitch, polyacrylonitrile, polycarbodiimide, polyimide, polybenzo are used. When at least one thermoplastic carbon precursor selected from the group consisting of azoles and aramids is used to obtain carbon fibers obtained by firing the thermoplastic carbon precursor, sea components are removed. At this time, as a pretreatment, the thermoplastic carbon precursor as an island component is stabilized to form a stabilized precursor molded body. Here, stabilization of the thermoplastic carbon precursor is a step necessary to obtain carbonized or graphitized carbon fiber, and when the thermoplastic resin is removed as the next step without performing this, Problems such as the thermal decomposition and fusion of the thermoplastic carbon precursor occur.

  As a stabilization method, a known method such as a gas flow treatment with oxygen or a solution treatment with an acidic aqueous solution can be used, but infusibilization under a gas flow is preferable from the viewpoint of productivity. As the gas component to be used, oxygen and / or from the viewpoint of permeability to the thermoplastic resin and adsorption to the thermoplastic carbon precursor, and from the point that the thermoplastic carbon precursor can be quickly infusibilized at low temperature. A mixed gas containing a halogen gas is preferred. Examples of the halogen gas include fluorine gas, chlorine gas, bromine gas, and iodine gas. Among these, bromine gas and iodine gas are particularly preferable. As a specific method of infusibilization under a gas stream, the temperature is 50 to 350 ° C., preferably 80 to 300 ° C., 5 hours or less, preferably 2 hours or less, and further 30 minutes or less in a desired gas atmosphere. Exposure to is preferred.

  In addition, the softening point of the thermoplastic carbon precursor contained in the precursor molded body is significantly increased by the infusibilization, and the softening point is preferably 400 ° C. or higher for the purpose of obtaining a desired carbon fiber. More preferably, the above is true.

  Next, the thermoplastic resin contained in the stabilized precursor molded body is removed and only the fibrous carbon precursor is separated. In this step, the thermal decomposition of the carbon fiber precursor is suppressed as much as possible, and the thermoplastic resin is removed. It is necessary to decompose and remove only the fibrous carbon precursor. Examples of the method for decomposing and removing the thermoplastic resin include a method for dissolving the thermoplastic resin with a solvent and a method for decomposing and removing the thermoplastic resin by thermal decomposition.

Finally, carbon fiber is produced by carbonizing or graphitizing the fibrous carbon precursor excluding the thermoplastic resin in an inert gas atmosphere. The resulting carbon fiber has a fiber diameter of 0.001 μm to 2 μm. It is preferable that it is 0.001 micrometer-1 micrometer.
Further, the material and dimensions of the single base plate used in the spinneret of the present invention are not particularly limited, and it is sufficient that no deformation or distortion occurs under the conditions of the polymer used.

  The cross-sectional shape of the fiber obtained by using the die of the present invention is not particularly limited, and is represented by a round shape, a triangular shape, a hollow shape, and a cross shape, and may be an aggregate having different cross sections. Moreover, the deformity and the hollowness are not particularly limited.

EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention does not receive any limitation by this.
In order to evaluate the degree of stretching of the island component, the aspect ratio of the island component (island phase fiber axial length (l) / island phase fiber cross-sectional diameter (d)) was determined by the following operation.
That is, the cut surface when the sample is cut at an arbitrary surface is observed using a scanning electron microscope (S-2400, manufactured by Hitachi, Ltd.), and the fiber diameter and fiber of island components dispersed in the sea phase The length was obtained and the aspect ratio of the island phase fiber was derived using these values.

  In addition, as a parameter for evaluating the stability of spinning, the base surface cleaning period was used. In order to prevent the occurrence of frequent bending and breakage of the discharged yarn due to the deterioration of polymer and additive substances that accumulate over time on the peripheral edge of the spinneret discharge hole during spinning, It is work to remove. In this example, the spinneret surface was observed every time foreign matter could be visually observed, but since the production of the composite yarn was interrupted during this nozzle surface cleaning, It can be said that the longer the interval until the nozzle surface is cleaned, the more stable spinning is performed.

Poly-4-methylpentene-1 (melting point: about 220 ° C.) is used as the sea component, and mesophase pitch (softening point: about 280 ° C.) is blended as the island component at a volume fraction of 10%. After melt-kneading using an extruder (KTX30, manufactured by Kobe Steel), the number of filaments is discharged from a capillary having a capillary diameter Dc = 0.1 mm and a capillary length Lc = 0.1 mm at a spinneret temperature of 345 ° C. Twenty yarns were produced at a take-up speed of 1200 m / min.
Table 1 shows the results of comparing the island phase fiber diameter as an additive component and the die surface cleaning period by changing the kind of die.

  As shown in the above table, it was confirmed that the additive component inside the fiber could be effectively stretched by gradually changing the shape of the spinneret channel. Moreover, it is estimated that the surface property of the fiber is improved and the deposits on the periphery of the discharge hole are reduced due to the extension of the base surface cleaning cycle time.

It is the figure which showed typically the flow-path structure of the nozzle | cap | die for mixed spinning used for the manufacturing method of this invention. It is the figure which showed typically the flow-path structure of the nozzle | cap | die for mixed spinning used for the manufacturing method of this invention. It is the figure which showed typically the nozzle | cap | die for mixed spinning used for the conventional manufacturing method. It is the figure which showed typically the cross section of the mixed spinning fiber obtained by the manufacturing method of this invention, and the internal structure when a quarter circle of this fiber was cut out.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Spinneret 2 Introduction hole 3 Constriction part 4 Capillary (pore)
5 Discharge hole 6 Resin inflow surface 7 Resin discharge surface 8 Additive component 9 Sea component Di Resin inflow portion diameter Dc Capillary diameter Lc Capillary length D Mixed spinning fiber diameter d Island phase fiber diameter l Island phase fiber length

Claims (8)

A spinning die used for producing a sea-island type mixed spinning fiber from a resin composition,
It is characterized by comprising a flow path that is combined in the order of an introduction hole for introducing a resin composition for forming a sea-island mixed spun fiber, a constriction, and a capillary and is continuously reduced in diameter in the resin discharge direction. A spinneret for mixed spinning.   The angle α formed between the hole wall surface and the central axis in the introduction hole portion that continuously decreases in diameter is 0 ° to 30 °, and in the restriction portion where the introduction hole portion and the capillary are connected, The angle β formed with the shaft is 10 to 60 degrees, and the Lc / Dc (capillary length / capillary diameter) of the capillary is 0.1 to 10, and the angles α and β of the introduction hole and the throttle part, respectively. The spinneret for mixed spinning according to claim 1, wherein becomes smaller continuously in the resin discharge direction. A method for producing a sea-island type mixed spinning fiber having a sea component and an island component, and removing the sea component from the sea-island type mixed spinning fiber to obtain the island component as an ultrafine fiber,
A pitch having a softening point of 50 ° C to 200 ° C higher than the softening point of the sea component, using a thermoplastic resin having a softening point of 50 ° C to 350 ° C as the sea component, which is incompatible with the sea component. And at least one thermoplastic carbon precursor selected from the group consisting of polyacrylonitrile, polycarbodiimide, polyimide, polybenzoazole, and aramids as an island component in a volume fraction (Vf) of 0.5% to 150%. After the addition, it is melt-kneaded, and is combined in the order of the introduction hole part, the throttle part and the capillary, and discharged and solidified from a die having a flow path continuously reduced in the resin discharge direction to obtain a sea-island type mixed spinning fiber. Then, the sea component of the sea-island type mixed spun fiber is removed to obtain the island component as an ultrafine fiber.   The angle α formed between the hole wall surface and the central axis in the introduction hole portion that continuously decreases in diameter is 0 ° to 30 °, and in the restriction portion where the introduction hole portion and the capillary are connected, The angle β formed with the shaft is 10 to 60 degrees, and the Lc / Dc (capillary length / capillary diameter) of the capillary is 0.1 to 10, and the angles α and β of the introduction hole and the throttle part, respectively. The spinneret for mixed spinning according to claim 3, wherein becomes smaller continuously in the resin discharge direction.   The production method according to claim 3, wherein the sea component is removed by subjecting the island component to a firing process under a condition that maintains the shape.   The method according to claim 3, wherein the sea component is removed by contacting the island component with a solution capable of dissolving the sea component under the condition that the shape of the island component is maintained.   The production method according to claim 3, wherein the aspect ratio (= island phase fiber length (l) / island phase fiber diameter (d)) of the island component in the mixed spun fiber is greater than 1 and less than 1 million.   The production method according to claim 3, wherein the sea component is polyethylene, poly-4-methylpentene-1 and / or a copolymer thereof.

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