JP6497506B2 - Method for producing ultrafine fiber of vinylidene fluoride resin and ultrafine fiber of vinylidene fluoride resin - Google Patents

Description

  The present invention relates to a method for producing a vinylidene fluoride resin ultrafine fiber and a vinylidene fluoride resin ultrafine fiber.

  The ultrafine fiber of vinylidene fluoride resin having a fiber diameter of less than 1 μm, that is, in the nanometer range (several nanometers to several hundred nanometers) is useful as a reinforcing material for various filters, electrolyte membranes for polymer electrolyte fuel cells, and the like. It is attracting attention as a future innovative material in a wide range of fields such as IT, biotechnology, and the environment.

  Patent Document 1 includes a step of producing a spinning solution by dissolving a vinylidene fluoride resin in a solvent, and a step of obtaining a hydrophobic polymer nanofiber web from the spinning solution by an electrospinning method (ES method). A method for manufacturing a membrane is described.

  In Patent Document 2, a vinylidene fluoride resin and another resin are mixed and melt-stretched, and the other resin mixed with the vinylidene fluoride resin is removed by a solvent to produce an ultrafine fibrous material. A method is described.

  Patent Document 3 describes that a nanofiber layer containing a vinylidene fluoride resin is produced by a melt blowing method or an electroblowing method.

Special table 2013-506830 gazette (announced February 28, 2013) Special Table 9-9721 Publication (announced January 7, 1997) Special table 2010-509508 gazette (March 25, 2010 publication)

  However, in the electrospinning method as described in Patent Document 1, the electroblowing method as described in Patent Document 3, and the method of manufacturing an ultrafine fiber as described in Patent Document 2 Then, an ultrafine fiber of polyvinylidene fluoride resin is manufactured using a solvent. For this reason, there is a problem that it is necessary to remove the solvent from the ultrafine fiber depending on the application.

  Moreover, in the melt blowing method as described in Patent Document 3, there is a problem that the ultrafine fibers manufactured from the vinylidene fluoride resin are not fused to each other, and it may be difficult to form a nonwoven fabric. .

  This invention is made | formed in view of said problem, The objective is to provide the method of manufacturing successfully the ultrafine fiber containing the vinylidene fluoride resin.

  In order to solve the above-described problems, a method for producing a vinylidene fluoride resin ultrafine fiber according to the present invention is a method for producing an infrared light flux while sending a raw filament containing a vinylidene fluoride resin in the length direction of the raw filament. The heated original filament is stretched by an air flow along the length direction.

  In the method for producing an ultrafine fiber of vinylidene fluoride resin according to the present invention, the air flow has an atmospheric pressure P2 in which the other end is placed rather than an atmospheric pressure P1 in which the one end of the original filament is placed. More preferably, it is caused by lowering.

  In the method for producing an ultrafine fiber of vinylidene fluoride resin according to the present invention, the original filament is more preferably an unstretched filament.

  In the method for producing an ultrafine fiber of vinylidene fluoride resin according to the present invention, the vinylidene fluoride resin is a homopolymer of vinylidene fluoride monomer or a copolymer containing 50% by mass or more of vinylidene fluoride monomer. More preferably.

  An ultrafine fiber of vinylidene fluoride resin produced by the method for producing an ultrafine fiber of vinylidene fluoride resin according to the present invention is also within the scope of the present invention.

  More preferably, the ultrafine fiber of the vinylidene fluoride resin according to the present invention has a β crystal ratio of 75% or more in the ultrafine vinylidene fluoride resin.

  In the ultrafine fiber of the vinylidene fluoride resin according to the present invention, the average fiber diameter of the vinylidene fluoride resin obtained by ultrafinening the vinylidene fluoride resin is more preferably 400 nm or less.

  According to the present invention, it is possible to successfully manufacture an ultrafine fiber containing a vinylidene fluoride resin.

It is a figure for demonstrating the outline of the manufacturing apparatus for manufacturing the ultrafine fiber which consists of vinylidene fluoride resin which concerns on one Embodiment of this invention. It is an enlarged view by the electron microscope of the ultrafine fiber which consists of a vinylidene fluoride resin. It is a graph which shows distribution of the fiber diameter of the ultrafine fiber which consists of vinylidene fluoride resin which concerns on one Embodiment of this invention. It is a graph which shows the result of DSC measurement in the ultrafine fiber and original filament which consist of vinylidene fluoride system resin concerning one embodiment of the present invention.

<Method for producing ultrafine fiber of vinylidene fluoride resin>
In the method of manufacturing a nanofiber (ultrafine fiber) according to an embodiment of the present invention, a raw filament containing a vinylidene fluoride resin is heated by an infrared light beam while being sent in the length direction of the raw filament, and heated. The original filament is stretched by an air flow along the length direction. The air flow along the length direction is preferably generated by lowering the atmospheric pressure P2 of the environment where the other end is placed, rather than the atmospheric pressure P1 of the environment where the one end of the original filament is placed. In the present embodiment, a case where an air flow is generated by a pressure difference will be described below as an example.

  The nanofiber manufacturing method according to an embodiment of the present invention uses a vinylidene fluoride resin without dissolving it in a solvent such as chloroform, unlike the ES method and electroblowing method, which are conventional nanofiber manufacturing methods. Therefore, solvent removal is unnecessary. For this reason, the nanofiber which can be used in the medical field | area where use of a harmful solvent is not desired can be manufactured. Therefore, it is possible to successfully manufacture nanofibers in which the original filament containing the vinylidene fluoride resin is ultrafine.

  Further, in the nanofiber manufacturing method according to an embodiment, after the original filament containing the vinylidene fluoride resin manufactured by melt spinning is drawn and the nanofiber is manufactured, the nanofiber can be fused to each other. it can. That is, according to the nanofiber manufacturing method according to an embodiment, a nonwoven fabric made of nanofibers can be successfully manufactured using a polyvinylidene fluoride resin that does not contain a solvent.

  Moreover, according to the manufacturing method of the nanofiber which concerns on one Embodiment, the nanofiber (ultrafine fiber) whose average fiber diameter is 500 nm or less can be manufactured. The nanofiber has a narrow fiber diameter distribution and a length of several meters or more, and such a nonwoven fabric made of nanofibers containing a vinylidene fluoride resin can be preferably produced.

  In the present specification, “nanofiber” means a fiber having an average fiber diameter of less than 1 μm.

[Vinylidene fluoride resin]
In this specification, vinylidene fluoride resin (simply referred to as “PVDF”) includes a homopolymer of vinylidene fluoride (VDF) and a copolymer of VDF and another monomer, There is no limit to the type and number of monomers contained in. Here, any other monomer may be used as long as it is copolymerizable with VDF. For example, fluorine monomers such as trifluoroethylene (TrFE), chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), and tetrafluoroethylene (TFE), and hydrocarbon monomers such as ethylene and propylene. Carboxyl group-containing monomers such as acrylic acid, and carboxylic acid anhydride group-containing monomers such as maleic anhydride, and more preferably, trifluoroethylene (TrFE) and the like can be mentioned. If it is such a monomer, the original filament which can manufacture nanofiber with a high ratio of (beta) crystal | crystallization can be obtained by making it copolymerize with VDF. Further, the ratio of β crystals in PVDF can be further increased by increasing the ratio of VDF to these other monomers or by copolymerizing TrFE or the like as VDF with other monomers.

  The PVDF used in the present invention may be one type of polymer or a mixture of two or more types of polymers. The content of the vinylidene fluoride monomer in the vinylidene fluoride copolymer, including the case of using a mixture of two or more polymers and a copolymer, is a content in the range of 50% by mass to 100% by mass. Preferably, the content is in the range of 60% by mass or more and 100% by mass or less, and more preferably in the range of 90% by mass or more and 100% by mass or less. If the content of vinylidene fluoride monomer in the vinylidene fluoride copolymer is in the range of 50% by mass or more and 100% by mass or less, a PVDF nanofiber having a β crystal ratio of 75% or more is manufactured. An original filament that can be obtained can be obtained.

  By using the original filament containing PDVF, nanofibers having a high β-crystal ratio can be suitably manufactured among the fluorine-containing resins. In particular, PVDF is more preferably composed of a homopolymer of VDF or a copolymer of VDF and TrFE. By producing a nanofiber using a VDF homopolymer or an original filament composed of a copolymer of VDF and TrFE, the ratio of β crystals in the nanofiber can be further increased. High piezoelectricity, pyroelectricity, and ferroelectricity can be provided. Therefore, it is expected that nanofibers that can be suitably used for medical applications and sensing applications can be manufactured.

  In addition, PVDF may contain additives, such as a coloring inhibitor, a phenol type stabilizer, a pigment | dye, and functional particles, as another component.

  A commercially available PVDF can be used. For example, commercially available powdery PVDF may be melted by heating to form a raw filament, and then used to produce nanofibers by the production method according to the present invention.

[Original filament]
The original filament is a filament containing PVDF and is used to form a nanofiber. The original filament is a substantially continuous fiber and is distinguished from a short fiber having a length of several millimeters to several tens of millimeters. The original filament is preferably a single fiber containing PVDF, but a multifilament in which several to several tens of fibers are aggregated may be used. The filament may have a core-sheath structure or a sea-island structure composed of two PVDFs having different compositions and molecular weights, or a core-sheath structure or a sea-island structure composed of PVDF and another resin. When a filament having a core-sheath structure formed by a combination of PVDF and another resin is adopted as the original filament, the original filament may be formed by PVDF at either the core or the sheath in the core-sheath structure. Similarly, when a filament having a sea-island structure is employed, the original filament may be formed by PVDF at either the sea part or the island part in the sea-island structure. Moreover, what was heat-processed previously can also be used for an original filament.

  The raw filament can be produced, for example, by melt spinning. The average fiber diameter of the original filament can be appropriately adjusted according to the conditions for stretching the original filament, but is preferably in the range of 10 μm to 1000 μm, for example, in the range of 50 μm to 800 μm. Is preferable, and most preferably in the range of 100 μm or more and 500 μm or less. When the average fiber diameter of the original filament is in the range of 10 μm or more and 1000 μm or less, it is possible to prevent the original filament from melting when heated by laser light (infrared light beam). Moreover, the PVDF nanofiber whose average fiber diameter is 400 nm or less can be manufactured suitably.

  The original filament may be pre-formed to an average fiber diameter in the range of 10 μm or more and 1000 μm or less by stretching the original filament, but it becomes an average fiber diameter in the range in an unstretched state. It is more preferable to use what is shaped like this. According to the manufacturing method which concerns on one Embodiment, the nanofiber of an average fiber diameter of 400 nm or less can be manufactured by using the unstretched PVDF original filament.

  In another aspect, according to the method for manufacturing a nanofiber according to an embodiment, a nanofiber having a high β crystal ratio can be manufactured without performing a pre-process for previously stretching the original filament.

〔manufacturing device〕
The manufacturing method of the nanofiber which concerns on one Embodiment can be implemented using the manufacturing apparatus shown to (a) of FIG.

  As shown in FIG. 1A, in the manufacturing apparatus, the original filament 1 containing PVDF is unwound from a state wound on the supply reel 11, and is guided to the orifice 14 through the comb 12. Here, the manufacturing apparatus may send the original filament 1 to the orifice 14 at a constant speed by the rotation of the supply reel 11, or may send the original filament 1 to the orifice 14 at a constant speed by the rotation of the feeding nip rollers 13a and 13b. .

  In addition, as shown to (a) of FIG. 1, before the entrance of the orifice 14 connected to the extending | stretching chamber 20, the original filament 1 open | released outside is set | placed on the atmosphere of atmospheric pressure as the atmospheric pressure P1.

  After the exit of the orifice 14, the stretching chamber 20 is placed in an environment having a pressure P2 lower than the pressure P1. The original filament 1 delivered to the orifice 14 is guided to the stretching chamber 20 together with high-speed air brought about by a pressure difference between the external pressure P1 and the pressure P2 of the stretching chamber 20.

  Here, as shown in FIGS. 1A and 1B, the original filament 1 passes inside the region M irradiated with the laser beam (infrared light beam) 30 irradiated from the laser oscillation device 15.

  The original filament 1 is stretched by being heated when passing through the region M and being tensioned by high-speed air caused by a pressure difference. Thereby, the nanofiber 2 is formed from the original filament 1. The formed nanofibers 2 are stacked on, for example, a conveyor and collected as a nanofiber aggregate or non-woven fabric.

  Note that the internal pressure P2 of the stretching chamber 20 can be adjusted by a duct 21 and a valve 22 communicating with a vacuum pump (not shown). Further, the stretching chamber 20 is provided with a barometer 23 and an output meter 16 for measuring the output of the laser beam 30 irradiated from the laser oscillation device 15.

(Other manufacturing equipment)
The manufacturing apparatus shown in FIG. 1 is only an example of an apparatus for manufacturing nanofibers. For example, it is equipped with a supply chamber that communicates with the pressurizing pump, and by incorporating the original filament, reel, comb, nip roller, orifice entrance side, etc. before the orifice entrance into the supply chamber, the atmospheric pressure of the environment before the orifice entrance It is also possible to manufacture nanofibers using a manufacturing apparatus capable of setting P1 to a condition other than atmospheric pressure.

  In addition, the manufacturing apparatus may be configured to focus laser light on the region M by reflecting the laser light with a mirror, or may be configured to irradiate the region M with laser light from a plurality of light sources.

[Production conditions]
In the nanofiber manufacturing method according to an embodiment, the atmospheric pressure difference between the atmospheric pressure P1 of the environment where one end of the original filament is placed and the atmospheric pressure P2 of the drawing chamber where the other end is placed, the environment of the atmospheric pressure P1 and the atmospheric pressure P2 By adjusting the diameter of the orifice that communicates with the drawing chamber, the output of the laser light that irradiates the original filament, the distance from the exit of the orifice to the center point of the region that irradiates the laser light, and the delivery speed of the original filament Manufacture nanofibers. By adjusting these conditions, a PVDF nanofiber having a high β crystal ratio can be manufactured, and a PVDF nanofiber having an average fiber diameter of 400 nm or less can be manufactured.

(Atmospheric pressure difference)
By reducing the atmospheric pressure P2 of the environment after the original filament is sent to the drawing chamber to be lower than the atmospheric pressure P1 of the environment before the original filament is sent to the drawing chamber, the original pressure generated by the pressure difference between the pressure P1 and the pressure P2 is generated. The original filament heated by the laser beam is stretched by an air flow along the length direction of the filament. Thereby, the flow of a high-speed gas flow can be stabilized and the nanofiber containing PVDF can be manufactured continuously.

  The atmospheric pressure P1 only needs to be higher than the atmospheric pressure P2, and is not limited. For example, the atmospheric pressure P1 may be standard atmospheric pressure.

  On the other hand, for example, when P1 is atmospheric pressure (101.3 kPa), the atmospheric pressure P2 of the environment where the end (the other end) of the original filament 1 that is sent from the orifice to the drawing chamber is placed is: , 95 kPa or less, more preferably 85 kPa or less. When the atmospheric pressure P1 is atmospheric pressure and the atmospheric pressure P2 is 95 kPa or less, nanofibers can be suitably manufactured. Moreover, when the atmospheric pressure P1 is atmospheric pressure, the average fiber diameter of the nanofibers can be further reduced by reducing the atmospheric pressure P2 to less than 85 kPa.

  From another point of view, in the nanofiber manufacturing method according to one embodiment, since nanofibers are manufactured using PVDF, nanofibers are suitable even when the pressure P2 is in the range of 50 kPa to 95 kPa. Can be manufactured. That is, even if the airflow obtained by the pressure difference between P1 and P2 does not exceed the speed of sound, the nanofiber can be suitably manufactured. For this reason, the energy required for manufacturing a nanofiber can be reduced. Moreover, the atmospheric pressure conditions for producing nanofibers can be easily managed. That is, the nanofiber can be easily manufactured.

(Orifice diameter)
In the nanofiber manufacturing method according to one embodiment, the nanofiber is manufactured by adjusting the diameter of the orifice that communicates the environment of the atmospheric pressure P1 and the environment of the atmospheric pressure P2.

  As shown in FIG. 1B, the orifice diameter is represented by an orifice diameter D which is an inner diameter of the orifice 14 on the outlet side. The orifice diameter D can be appropriately adjusted depending on the fiber diameter of the original filament, and is not limited. For example, the orifice diameter D is 1.05 times or more the fiber diameter d of the original filament 1. It is preferable that the diameter is within a range of 10 times or less. Moreover, the nanofiber with a smaller average fiber diameter can be manufactured by increasing the magnification of the orifice diameter D with respect to the fiber diameter d of the original filament 1 shown in FIG.

(Laser light)
In the nanofiber manufacturing method according to one embodiment, the nanofiber is manufactured by adjusting the output of the laser light applied to the original filament.

  The laser light is an infrared light beam having a wavelength of 0.7 μm to 100 μm. Examples of the laser light include a carbon dioxide laser with a wavelength of 10.6 μm and a YAG (yttrium, aluminum, garnet) laser with a wavelength of 1.06 μm. By irradiating with laser light, PVDF can be suitably heated and melted. Here, the output of the laser beam applied to the original filament can be adjusted as appropriate depending on the fiber diameter of the original filament to be used, and is not limited. For example, the average fiber diameter of 10 μm or more and 1000 μm or less is used. When producing a nanofiber using an original filament, it is preferable to irradiate laser light having an output within a range of 1 W or more and 100 W or less, and to irradiate laser light having an output within a range of 5 W or more and 30 W or less. More preferred. By irradiating a laser beam having an output within a range of 1 W or more and 100 W or less, the center of the original filament can be heated by the laser beam. Moreover, by irradiating the original filament containing PVDF with laser light having an output in the range of 1 W or more and 100 W or less, a PVDF nanofiber having an average fiber diameter of 400 nm or less can be suitably manufactured. . As shown in FIG. 1B, the laser beam is irradiated toward the region M through which the original filament 1 passes.

(Area irradiated with laser light)
As shown in FIG. 1B, in the nanofiber manufacturing method according to an embodiment, the distance L from the exit of the orifice 14 to the center point of the region M where the original filament 1 is irradiated with laser light is adjusted.

  The distance L is appropriately adjusted according to the beam diameter and output of the laser irradiated to the original filament, the atmospheric pressure difference between P1 and P2, and the like, but is not limited. For example, from the exit of the orifice to the center point of the region irradiated with the laser light The distance L is preferably in the range of 0.1 mm or more and 10.0 mm or less, and more preferably in the range of 0.2 mm or more and 8.0 mm or less. If the distance L is in the range of 0.1 mm or more and 10.0 mm or less, nanofibers can be suitably manufactured from the original filament containing PVDF. Further, by shortening the distance L, it is possible to manufacture nanofibers having a smaller average fiber diameter.

  The beam diameter of the laser can be appropriately adjusted in consideration of the laser output and the distance L, but is preferably about 1 mm, for example.

(Feeding speed)
In the nanofiber manufacturing method according to one embodiment, nanofibers are manufactured by adjusting the delivery speed at which the original filament is delivered in the length direction to the region irradiated with laser light.

  The delivery speed of the original filament is appropriately adjusted according to the pressure difference between P1 and P2, the output of the laser light applied to the original filament, the orifice diameter, and the distance from the exit of the orifice to the center point of the area irradiated with the laser light. However, the speed is preferably within a range of 0.001 m / min or more and 5.0 m / min or less, and preferably within a range of 0.03 m / min or more and 0.8 m / min or less. More preferably, the speed is most preferably in the range of 0.05 m / min to 0.5 m / min.

  The feed speed may be adjusted by adjusting the rotation speed of the supply reel 11 shown in FIG. 1A, or may be adjusted by adjusting the rotation speed of the feeding nip rollers 13a and 13b. Also good. The feeding speed may be adjusted by either the supply reel or the feeding nip roller according to the type of the original filament to be stretched. For example, when the original filament is an original filament composed of a single fiber, the original filament is drawn into the orifice due to the pressure difference between P1 and P2, and therefore the original filament is preferably adjusted by adjusting the rotation speed of the supply reel. The filament can be sent out.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

[Example 1]
Polyvinylidene fluoride KF # 1300 (manufactured by Kureha Co., Ltd.) was used to produce unstretched filaments (diameter 200 μm) by melt spinning, and the output of laser light (infrared light flux) was changed to produce nanofibers. The crystallinity and β-crystal ratio (%) of the drawn filament and the nanofiber produced at each laser output were evaluated.

  The nanofiber was manufactured using the manufacturing apparatus shown in FIG. The orifice diameter was set to 0.5 mm, and the distance from the exit of the orifice to the center point of the region irradiated with laser light (distance L in FIG. 1B) was set to 1.5 mm. P1 is atmospheric pressure, and the pressure P2 in the chamber (stretching chamber) was set to 80 kPa. The feed speed of the original filament was set to 0.2 m / min.

  The output of the laser beam for heating the original filament was 8 W, 10 W, 20 W, and 30 W. Nanofibers were produced with the respective laser outputs and evaluated.

  The β crystal ratio was measured by the following method.

Measurement of β crystal ratio (%):
It was calculated based on the following formula using IR (reference: Journal of Polymer Science: Part B: Polymer Physics Vol 32 859-870 (1994)).
β crystal ratio (%) = β / (1.3α + β)
Absorbance of α crystal at α = 766 cm−1 β Absorbance of β crystal at 840 cm−1 The results are shown in Table 1 below.

  As shown in Table 1, the nanofiber produced by irradiating laser light with an output of 8 W to 30 W while the β crystal ratio in the original filament having an average fiber diameter of 200 μm is 26.8% Was confirmed to have a β crystal ratio of 75% or more.

  2A to 2D are electron micrographs of nanofibers manufactured under each laser output condition in Table 1. FIG. (A) to (d) in FIG. 2 are photographs obtained by magnifying the nanofibers obtained under the conditions of laser outputs of 8 W, 10 W, 20 W, and 30 W to 10000 times. 2A to 2D, it was confirmed that nanofibers having a fiber diameter of less than 1 μm were obtained.

  FIGS. 3A to 3D are graphs showing the average fiber diameter distribution of nanofibers manufactured under each laser output condition in Table 1. FIG. As shown in FIGS. 3A to 3D, it was confirmed that the average fiber diameter was 500 μm or less under any laser output condition. In particular, the nanofibers manufactured under conditions where the laser output is 10 W to 30 W have an average fiber diameter of about 300 nm, and the difference between the maximum and minimum fiber diameters is smaller than that when the laser output is 8 W. It was confirmed to be smaller.

  FIG. 4 shows a graph obtained by measuring the differential scanning calorimetry (DSC) of the nanofiber manufactured under each laser output condition in Table 1. Note that “Original” in FIG. 4 refers to an unstretched original filament (200 μm) produced by KF # 1300. FIG. 4 shows a tendency that the endothermic peak around 173.4 ° C. in the original filament of KF # 1300 becomes smaller as the nanofiber is manufactured under a condition where the laser output is high. Further, in all the nanofibers manufactured with a laser output of 8 W, an endothermic peak is confirmed around 160 ° C. In other words, it can be confirmed that the crystal structure transition occurs by irradiating the unstretched KF # 1300 original filament with a laser having an output of 8 W or more to produce a nanofiber.

[Example 2]
Using polyvinylidene fluoride KF # 1300 (manufactured by Kureha Co., Ltd.), a drawn filament (diameter: 200 μm) is produced as an original filament by melt spinning, P1 is set to atmospheric pressure, P2 in the chamber (drawing chamber), and the filament Nanofibers were manufactured by changing the position of laser light irradiation.

  The nanofiber was manufactured using the manufacturing apparatus shown in FIG. The orifice diameter was set to 0.5 mm, the laser output was set to 10 W, and the feed rate of the original filament was set to 0.1 m / min. For each condition where the distance L shown in (b) of FIG. 1 is 0.5 mm, 1.0 mm, 1.5 mm, and 2.0 mm, the nanofiber is formed under the condition that the atmospheric pressure P2 in the stretching chamber is 40 kPa, 50 kPa, and 60 kPa. Manufactured and evaluated whether or not nanofibers can be manufactured. Whether or not nanofibers can be manufactured under each condition is evaluated by visual observation and SEM (scanning electron microscope) observation. Nanofibers can be manufactured by evaluating those that were able to manufacture nanofibers as “◯”. Those not present were evaluated as “x”.

  The results are shown in Table 2 below.

  As shown in Table 2, it was confirmed that nanofibers can be suitably manufactured under the conditions where the pressure P2 is 50 kPa or less and the distance L is any condition. Further, it was confirmed that nanofibers can be preferably manufactured by setting the distance L to 1.0 mm or less even under the condition where the atmospheric pressure P2 is 60 kPa.

Example 3
Using polyvinylidene fluoride KF # 1300 (manufactured by Kureha Co., Ltd.), a drawn filament (diameter 120 μm) is produced by melt spinning as an original filament, and the pressure P2 in the chamber (drawing chamber), the diameter of the orifice, and The distance L shown in (b) was changed to manufacture nanofibers, and the average fiber diameter of the obtained nanofibers was measured.

  The nanofiber was manufactured using the manufacturing apparatus shown in FIG. The laser output was set to 30 W, and the feed speed of the original filament was set to 0.1 m / min. P1 is atmospheric pressure. The conditions and results of the orifice diameter, distance L, and atmospheric pressure P2 are shown in Table 3 below.

  As shown in Table 3, it was confirmed that the average fiber diameter of the nanofibers tends to be smaller when the orifice diameter is 0.5 mm than when the orifice diameter is 0.3 mm. Moreover, it has confirmed that the nanofiber with a smaller average fiber diameter can be manufactured, so that the distance L is short. Note that nanofibers could not be obtained under the conditions of an orifice diameter of 0.3 mm, a distance L of 2.0 mm, and a pressure of 60 kPa in the chamber.

Example 4
Polyvinylidene fluoride KF # 1300 (manufactured by Kureha Co., Ltd.) was used to produce a drawn filament (120 μm in diameter) by melt spinning as the original filament, and the nanofilament was manufactured by changing the feed rate of the original filament, and the average fiber The diameter was measured.

  The nanofiber was manufactured using the manufacturing apparatus shown in FIG. The orifice diameter was set to 0.5 mm, the distance L to 1.5 mm, and the laser output to 30 W. P1 was atmospheric pressure, and the atmospheric pressure P2 in the chamber was set to 30 kPa. Nanofibers were produced under the conditions of the original filament feed rates of 0.05 mm / min, 0.1 mm / min, and 0.5 mm / min. The results are shown in Table 4 below.

  As shown in Table 4, it was confirmed that nanofibers having an average fiber diameter of 300 nm or less can be produced regardless of the feed rate of the original filament.

Example 5
Nanofibers were manufactured using the heat-treated raw filaments, and the average fiber diameter was measured.

  First, a drawn filament (diameter: 120 μm) is prepared by melt spinning using KF # 1300 (manufactured by Kureha Co., Ltd.), and then an unheated filament (untreated), 30 ° C., 30 ° C. using the drawn filament. A filament heated for 1 minute (treatment 1) and a filament heated at 140 ° C. for 30 minutes (treatment 2) were prepared.

  The nanofiber was manufactured using the manufacturing apparatus shown in FIG. The orifice diameter was set to 0.5 mm, the distance L was set to 1.5 mm, the laser output was set to 20 W, and the feed rate of the original filament was set to 0.1 mm / min. P1 was atmospheric pressure, and the atmospheric pressure P2 in the chamber was set to 30 kPa. The average fiber diameter of the nanofibers obtained using each original filament is shown in Table 5 below.

  As shown in Table 5, it was confirmed that even if the original filament was heated in advance, the nanofiber could be suitably produced.

Example 6
Polyvinylidene fluoride KF # 1300 (manufactured by Kureha Co., Ltd.) is used to produce unstretched filaments (diameter 200 μm) by melt spinning, and the conditions of laser output, raw filament delivery speed, and atmospheric pressure P2 in the chamber are changed. The nanofiber was manufactured, and the average fiber diameter of the obtained nanofiber was measured.

  The nanofiber was manufactured using the manufacturing apparatus shown in FIG. The orifice diameter was set to 0.5 mm, and the distance L from the exit of the orifice to the center point of the region irradiated with laser light was set to 1.5 mm. P1 is atmospheric pressure. Table 6 below shows the conditions of the laser output, the delivery speed, and the atmospheric pressure P2 in the chamber, and the average fiber diameter of the nanofibers obtained under these conditions.

  As shown in Table 6, nanofibers could not be manufactured under conditions where the laser output was 5 W, the delivery speed was 0.1 mm, and the atmospheric pressure in the chamber was 60 kPa. However, the pressure in the chamber was reduced to 30 kPa from the conditions under which the nanofiber could not be manufactured, the conditions under which the laser output was increased to 10 W, and the condition under which the nanofiber could not be manufactured. It has been confirmed that nanofibers can be suitably manufactured under the manufacturing conditions.

Example 7
Using polyvinylidene fluoride KF # 1300 (manufactured by Kureha Co., Ltd.), an unstretched filament (diameter: 200 μm) is prepared by melt spinning, and the distance L from the exit of the orifice to the center point of the region irradiated with the laser beam, and The nanofiber was manufactured by changing the pressure P2 in the chamber, and the average fiber diameter of the obtained nanofiber was measured.

  The nanofiber was manufactured using the manufacturing apparatus shown in FIG. The orifice diameter was set to 0.5 mm, the laser output was set to 10 W, and the feed rate of the original filament was set to 0.2 m / min. P1 is atmospheric pressure. Table 7 below shows the conditions of the distance L and the atmospheric pressure P2 in the chamber, and the average fiber diameter of the nanofibers obtained under these conditions.

  As shown in Table 7, it was confirmed that even if the distance L was changed, the nanofiber could be suitably manufactured.

Example 8
Polyvinylidene fluoride KF # 1300 (manufactured by Kureha Co., Ltd.) is used to produce unstretched filaments (diameter 200 μm) by melt spinning, to produce nanofibers by changing the orifice diameter and pressure P2 in the chamber, The average fiber diameter of the obtained nanofiber was measured.

  The nanofiber was manufactured using the manufacturing apparatus shown in FIG. The laser output was set to 10 W, the distance L was set to 1.5 mm, and the feed speed of the original filament was set to 0.2 m / min. P1 is atmospheric pressure. Table 8 below shows the orifice diameter, the conditions of the pressure P2 in the chamber, and the average fiber diameter of the nanofibers obtained under these conditions.

  As shown in Table 8, even when an unstretched filament was used as the original filament, it was confirmed that the average fiber diameter could be reduced by increasing the orifice diameter.

Example 9
Using polyvinylidene fluoride KF # 1300 (manufactured by Kureha Co., Ltd.), an unstretched filament (diameter: 200 μm) is prepared by melt spinning, and the distance L from the exit of the orifice to the center point of the region irradiated with the laser beam, and The nanofiber was manufactured by changing the pressure P2 in the chamber, and the average fiber diameter of the obtained nanofiber was measured.

  The nanofiber was manufactured using the manufacturing apparatus shown in FIG. The orifice diameter was set to 1.0 mm, the laser output was set to 10 W, and the feed rate of the original filament was set to 0.2 m / min. P1 is atmospheric pressure. Table 9 below shows the conditions of the distance L and the atmospheric pressure P2 in the chamber, and the average fiber diameter of the nanofibers obtained under these conditions.

  As shown in Table 9, it was confirmed that even if the distance L was changed, the nanofiber could be suitably manufactured.

  As described above, according to Example 1, it was confirmed that according to the nanofiber manufacturing method of the present invention, a nanofiber having a β crystal ratio of 75% or more can be manufactured using PVDF. Further, according to Examples 1 to 9, a nanofiber made of PVDF having an average fiber diameter of 700 nm or less, in particular, an average fiber diameter of 400 nm or less by adjusting each condition such as orifice diameter and laser output. I was able to confirm that

  INDUSTRIAL APPLICATION This invention can be utilized for manufacture of the nanofiber of vinylidene fluoride resin.

1 Original filament 2 Nanofiber (extra fine fiber)
30 Laser light (infrared luminous flux)

Claims (7)

Was heated by an infrared light beam while feeding an original filament that contains vinylidene fluoride resin in a longitudinal direction of the original filament, and stretching by a gas stream along the heated the raw filaments wherein the length direction, said original filament A method for producing an ultrafine fiber of vinylidene fluoride resin, wherein the ratio of β crystals in the vinylidene fluoride resin is increased . 2. The method for producing an ultrafine fiber according to claim 1, wherein the vinylidene fluoride resin is a homopolymer of a vinylidene fluoride monomer or a copolymer containing 50% by mass or more of a vinylidene fluoride monomer. . The method for producing an ultrafine fiber according to claim 2, wherein the proportion of β crystal in the ultrafine vinylidene fluoride resin is 75% or more . The method of manufacturing an ultrafine fiber according to any one of claims 1 to 3, wherein the infrared light beam is laser light, and an output thereof is 8W to 30W. The airflow claims 1 to 4, characterized in that said than pressure P1 of the environment in which one end of the original filament is placed causes by lowering the air pressure P2 of the environment in which the other end is placed The manufacturing method of the ultrafine fiber as described in any one of these . The method for producing an ultrafine fiber according to any one of claims 1 to 5, wherein the original filament is an unstretched filament . The method for producing an ultrafine fiber according to any one of claims 1 to 6, wherein the ultrafine fiberized vinylidene fluoride resin has an average fiber diameter of 400 nm or less .