JP4446748B2 - Manufacturing method of fiber assembly - Google Patents

Description

  The present invention relates to a method for producing a fiber assembly.

  If the fiber diameter of the fibers constituting the fiber assembly is small, the fiber assembly is configured because it has excellent performance such as separation performance, liquid retention performance, wiping performance, concealment performance, insulation performance, or flexibility. The fiber diameter of the fiber is preferably small. As a method for producing a fiber aggregate composed of fibers having such a small fiber diameter, the spinning dope is extruded from a nozzle, and an electric field is applied to the extruded spinning dope to stretch the spinning dope to obtain a fiber having a small fiber diameter. A so-called electrostatic spinning method is known in which a fiber assembly is collected.

  More specifically, “a step of producing a polymer solution in which a polymer is dissolved using a volatile solvent as a solvent, a step of spinning the polymer solution by a charge-induced spinning process, and the accumulation on the collector. A method for producing a fine fibrous polymer web comprising the step of obtaining a fine fibrous polymer web, wherein the relative humidity of the operating space of the charge-induced spinning process is 0 to 40%. Method "is disclosed (Patent Document 1). This method is certainly a method that can be stably spun by setting the relative humidity within this range, but there is a large variation in the fiber diameter of the resulting fine fibers, and a fiber assembly having the desired performance. There was a problem that the body could not be made.

JP 2002-249966 A (Claim 4 etc.)

  The present invention has been made for the purpose of solving the above-mentioned problems, and an object of the present invention is to provide a method capable of producing a fiber assembly with little variation in fiber diameter, that is, with a uniform fiber diameter.

  The invention according to claim 1 of the present invention is directed to “a method for producing a fiber assembly by directly collecting fibers spun by an electrospinning method using a spinning stock solution in which a resin is dissolved in a solvent. As a main component, the solubility in water is 100 g / 100 ml or more, and the spinning space by the electrospinning method has a predetermined relative humidity of 40% or less relative humidity and a relative of ± 2% of the predetermined relative humidity. It is a process for producing a fiber assembly, which is carried out in a state where the humidity is maintained. The present inventors have found that a solvent having a solubility in water of 100 g / 100 ml or more tends to take in water, and the taken-in water acts as a poor solvent for the resin of the spinning stock solution, so that the solubility of the resin is lowered and the viscosity of the spinning stock solution Spinning, and gelation and coagulation are likely to occur, so the relative humidity changes and the amount of water taken into the solvent changes, so the viscosity of the spinning dope also changes. It was found that the fiber diameter would change even if it was applied to the stock solution. Furthermore, it has also been found that the degree of influence is constant if the relative humidity is within a certain range. Therefore, in the present invention, by performing electrostatic spinning in a state where the relative humidity is maintained at a predetermined relative humidity of 40% or less and a relative humidity of ± 2% of the predetermined relative humidity, a spinning dope with relative humidity is obtained. By making the influence on the fiber constant and making the influence on the fiber diameter constant, it becomes possible to produce a fiber assembly having a desired fiber diameter and a uniform fiber diameter.

  The invention according to claim 2 of the present invention is such that “the solvent mainly used for the spinning dope is a solvent selected from N, N-dimethylformamide, N, N-dimethylacetamide, and N-methyl-2-pyrrolidone”. It is a manufacturing method of the fiber assembly according to claim 1 characterized in that it is. Even if the solvent reaches a saturated vapor pressure near room temperature, it only has a concentration that is sufficiently lower than the lower limit of explosion, and even if spark discharge occurs during electrospinning, it will explode. This is a suitable solvent because there is little concern about the problem. In addition, these solvents can be suitably used because they have a relatively high solubility of the resin, and do not have a very high vapor pressure and do not volatilize rapidly.

  According to a third aspect of the present invention, “a closed space is formed so as to surround the spinning space by the electrostatic spinning method, and a gas having a predetermined relative humidity is supplied to the closed space with a constant air volume. The method for producing a fiber assembly according to claim 1 or 2, characterized in that. Thus, by setting the spinning space as a closed space, the electrostatic spinning method can be easily performed in a state where the relative humidity is maintained at ± 2% of the predetermined relative humidity. In addition, in such a closed space, the vapor concentration of the solvent in the spinning space becomes higher and higher, the evaporation of the solvent is suppressed, the fiber diameter becomes thin, and the fiber diameter tends to vary. In this case, since the vapor concentration of the solvent reaches saturation and it becomes difficult to perform electrospinning, the gas having the predetermined relative humidity is supplied to the closed space with a constant air volume, so that spinning is performed. It is possible to stably produce a fiber assembly composed of fibers having a desired fiber diameter with a constant fiber vapor concentration in the space and a uniform fiber diameter.

  According to the method for producing a fiber assembly of the present invention, a fiber assembly having a desired fiber diameter and a uniform fiber diameter can be produced.

  The method for producing a fiber assembly of the present invention will be described with reference to FIG. 1 which is a conceptual schematic cross-sectional view of a production apparatus capable of performing the method for producing a fiber assembly.

  The production apparatus of FIG. 1 includes a spinning stock solution supply device 1 that can supply a spinning stock solution to a nozzle 2, a nozzle 2 that discharges the spinning stock solution supplied from the spinning stock solution supply device 1, and a fiber that is discharged from the nozzle 2 and drawn by an electric field. In order to form an electric field between the grounded collector 3, the nozzle 2 and the grounded collector 3, a voltage applying device 4 capable of applying a voltage to the nozzle 2, the nozzle 2 and the collector 3 Are provided, a gas supply device 7 capable of supplying a gas having a predetermined relative humidity to the spinning vessel 6, and an exhaust device 8 capable of exhausting the gas in the spinning vessel 6.

  When a fiber assembly is manufactured using such a manufacturing apparatus, first, a spinning dope is prepared. This spinning solution is a solution in which a resin that can be electrospun is dissolved in a solvent. Resin is not particularly limited, for example, polyethylene glycol, partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol, polyvinyl pyrrolidone, polylactic acid, polyglycolic acid, polyacrylonitrile, polymethacrylic acid, polymethyl methacrylate, polycarbonate, Polystyrene, polyamide, polyimide, polyethylene, polypropylene, or the like can be used. Resins other than those exemplified above can also be used, and a solution in which two or more resins including those other than those exemplified are dissolved in a solvent (that is, a spinning dope) can also be used.

  The main solvent of the spinning dope is a solvent having a solubility in water of 100 g / 100 ml or more (hereinafter sometimes referred to as “main solvent”). Such a main solvent is easy to take up moisture, and the taken-in moisture acts as a poor solvent for the resin, lowers the solubility of the resin, increases the viscosity of the spinning dope, and further tends to cause gelation and coagulation. Since the viscosity of the spinning dope also changes as the amount of water taken into the main solvent changes, the fiber diameter is likely to change even when a constant electric field is applied to the spinning dope. This tendency is more prominent as the solubility in water increases, and the main solvent that is completely miscible with water is most susceptible. In the present invention, by controlling the relative humidity, even if a main solvent that makes such an effect constant and is completely miscible with water is used, a fiber assembly having a uniform fiber diameter is obtained. Can be manufactured. The “solubility in water” refers to a dripping amount immediately before the mixed solution becomes cloudy or separated by adding dropwise the solvent to 100 g of pure water while stirring. Further, “mainly” means that it occupies 50% or more of the mass of the solvent.

  The main solvent varies depending on the resin, and is not particularly limited. For example, acetone, methanol, ethanol, propanol, isopropanol, tetrahydrofuran, dimethyl sulfoxide, 1,4-dioxane, pyridine, N, N- Examples thereof include dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, acetonitrile, formic acid and the like. Among these, N, N-dimethylformamide, N, N-dimethylacetamide, and N-methyl-2-pyrrolidone have concentrations that are sufficiently lower than the lower explosion limit even if they reach saturation vapor pressure near room temperature. Of course, even if spark discharge occurs during electrostatic spinning, there is little risk of explosion, and these main solvents are relatively high in resin solubility and vapor pressure is not so high. Since it does not volatilize rapidly, it can be suitably used. In addition, as long as the solubility in water is 100 g / 100 ml or more, main solvents other than those illustrated can be used. Further, the total amount of two or more kinds of solvents (including solvents other than the main solvents exemplified above) having a solubility in water of 100 g / 100 ml or more and different compositions is 50% of the total mass of the solvent constituting the spinning dope. The mixed solution which occupies the above can also be used as a main solvent.

  The solvent constituting a part of the spinning dope of the present invention may contain a solvent having a solubility in water of less than 100 g / 100 ml (hereinafter sometimes referred to as “secondary solvent”) in addition to the main solvent. . More specifically, the co-solvent includes toluene, benzene, cyclohexane, cyclohexanone, carbon tetrachloride, methylene chloride, chloroform, trichloroethane, ethylene carbonate, diethyl carbonate, propylene carbonate, and the like.

The spinning dope of the present invention is a solution obtained by dissolving the resin as described above in a main solvent (there may include a subsolvent), but the concentration at that time depends on the composition of the resin, the molecular weight of the resin, the main solvent, etc. Since it varies, it is not particularly limited, but from the viewpoint of applicability to electrospinning, the concentration is preferably such that the viscosity is in the range of 10 to 5000 mPa · s, and in the range of 20 to 4000 mPa · s. More preferably, the concentration is such that If the viscosity is less than 10 mPa · s, the main solvent does not evaporate and tends to be in a fibrous state, and if the viscosity exceeds 5000 mPa · s, the spinning dope becomes difficult to be stretched and tends to be in a fibrous state. It is. The “viscosity” refers to a value at a shear rate of 100 s ⁻¹ measured at a temperature of 25 ° C. using a viscosity measuring device.

  Such a spinning dope is supplied to the nozzle 2 by the spinning dope supply apparatus 1. The supplied spinning dope is pushed out from the nozzle 2 and is subjected to a drawing action by an electric field between the grounded collector 3 and the nozzle 2 applied by the voltage application device 4 and is directed toward the collector 3 while being fiberized. Flying (so-called electrostatic spinning method). The flying fibers are directly accumulated on the collecting body 3 to form a fiber assembly. In addition, although the spinning dope supply apparatus 1 is not specifically limited, For example, a syringe pump, a tube pump, a dispenser, etc. can be used.

  The pushing direction of the spinning dope from the nozzle 2 in FIG. 1 is a direction orthogonal to the gravity and the direction of the collecting body 3, so that the spinning dope does not drop on the collecting body 3. However, the direction in which the spinning solution is pushed out from the nozzle 2 may be different from that in FIG.

  The diameter of the nozzle 2 for extruding the spinning dope is not particularly limited because it varies depending on the fiber diameter of the fiber to be obtained. For example, when the fiber diameter is 0.7 μm or less, the nozzle The diameter (inner diameter) of 2 is preferably about 0.1 to 2.0 mm.

  The nozzle 2 may be made of metal or non-metal. If the nozzle 2 is made of metal, the nozzle 2 can be used as one electrode by applying a voltage from the voltage application device 4. If the nozzle 2 is made of non-metal, the inside of the nozzle 2 By applying an electrode to the inner electrode and applying a voltage to the internal electrode from the voltage application device 4, an electric field can be applied to the extruded spinning solution.

  In FIG. 1, a voltage is applied to the nozzle 2 by the voltage application device 4 and an electric field is formed by grounding the collector 3. However, contrary to FIG. 1, the nozzle 2 is grounded and captured. An electric field may be formed by applying a voltage to the collector 3, or a voltage may be applied to both the nozzle 2 and the collector 3, but an electric field may be formed by applying a potential difference. The electric field varies depending on the fiber diameter of the fiber, the distance between the nozzle 2 and the collection body 3, the main solvent of the spinning dope, the viscosity of the spinning dope, and is not particularly limited, but is 0.2 to 5 kV. / Cm is preferred. When the electric field strength exceeds 5 kV / cm, there is a tendency that dielectric breakdown of air tends to occur. When the electric field strength is less than 0.2 kV / cm, there is a tendency that the spinning dope is not sufficiently stretched and hardly forms a fiber shape.

  The voltage application device 4 is not particularly limited, and for example, a DC high voltage generator or a Van de Graf electromotive machine can be used. The applied voltage is not particularly limited as long as the electric field strength can be set as described above, but is preferably about 5 to 50 KV.

  The polarity of the voltage to be applied may be either positive or negative, but the nozzle 2 side has a positive potential so that the fiber spread is suppressed and the fiber aggregate in which the fibers are uniformly dispersed can be easily manufactured. It is preferable to do so. In particular, it is preferable to ground the collector 3 and apply the nozzle 2 positively so that the nozzle 2 has a positive potential so that corona discharge during voltage application can be easily suppressed.

  Although the collection body 3 in FIG. 1 is a drum, it should just be a thing which can collect a fiber, and is not specifically limited. For example, a non-woven fabric, a woven fabric, a knitted fabric, a net, a flat plate, or a belt made of a conductive material made of metal or carbon, or a non-conductive material made of an organic polymer can be used as the collector 3. In some cases, a liquid such as water or an organic solvent can be used as the collector 3.

As shown in FIG. 1, when the collector 3 is used as the other electrode, the collector 3 is preferably made of a conductive material (for example, made of metal) having a volume resistance of 10 ⁹ Ω or less. On the other hand, when the conductive material is disposed as the counter electrode behind the collector 3 as viewed from the nozzle 2 side, the collector 3 does not necessarily need to be made of a conductive material. When the counter electrode is arranged behind the collector 3 as in the latter case, the collector 3 and the counter electrode may be in contact with each other or may be separated from each other.

  In FIG. 1 in which the production method of the present invention can be carried out, the electrostatic spinning method as described above uses a nozzle 2 and a collecting body 3 installed in a spinning vessel 6, and a gas having a predetermined relative humidity is supplied to the spinning vessel 6. Is supplied at a constant air volume using the gas supply device 7, so that the spinning space 5 between the nozzle 2 and the collecting body 3 has a predetermined relative humidity of 40% or less relative humidity and ± 2 of the predetermined relative humidity. %, The gas in the spinning vessel 6 can be discharged using the exhaust device 8. Therefore, even with a spinning stock solution using a main solvent that easily takes in moisture, the influence of relative humidity can be made constant, and the influence of relative humidity on the spinning stock solution can be made constant. A uniform fiber assembly having a desired fiber diameter can be produced.

  As described above, the relative humidity of the gas supplied from the gas supply device 7 is 40% or less because the spinning stock solution takes in moisture, the resin solubility decreases, the spinning stock viscosity increases, and gelation or coagulation occurs. This is because the influence of is relatively small and can be made into a fiber. The degree of relative humidity of the gas supplied from the gas supply device 7 depends on the spinning stock solution (that is, the main solvent or resin) in addition to the change of the fiber diameter depending on the relative humidity as described above. Therefore, it can be experimentally determined by performing spinning at various relative humidities using a spinning solution to be spun. More specifically, electrostatic spinning is performed on the spinning solution to be spun in a state where the relative humidity is constant (± 1%), and the fiber diameter obtained under the conditions is confirmed. This operation is performed by changing the relative humidity to a certain level, and the relationship between the relative humidity and the fiber diameter is grasped. From this result, the relative humidity necessary to obtain the desired fiber diameter can be determined.

  For example, a manufacturing apparatus as shown in the schematic schematic cross-sectional view of FIG. 5 (the manufacturing apparatus of FIG. 1 except that the collector 3 is an aluminum plate 11 with an aluminum foil and that the position of the exhaust device 8 is different). 2), and using a spinning stock solution in which polyacrylonitrile having a weight average molecular weight of 420,000 was dissolved in N, N-dimethylformamide so as to have a concentration of 10 mass%, from a stainless steel nozzle 2 having an inner diameter of 0.4 mm. A fiber assembly was formed by accumulating the spun fibers on an aluminum plate 11 having an aluminum foil attached and disposed at a position 10 cm away. The fiber assembly was formed in a state where the relative humidity of the spinning space 5 was maintained at 20 ± 1%, 25 ± 1%, 30 ± 1%, 35 ± 1%, and 40 ± 1%. And the average fiber diameter of the fiber assembly manufactured at each relative humidity was measured. The result was as shown in FIG. As can be seen from FIG. 6, when it is desired to produce a fiber assembly having an average fiber diameter of 0.3 μm, the relative humidity should be 20.9%. The average fiber diameter is an arithmetic average value obtained by taking electron micrographs on both surfaces of the fiber assembly, measuring the fiber diameter (50 per surface) from each electron micrograph.

  In the present invention, it is important to maintain a relative humidity of ± 2% of a predetermined relative humidity. As described above, when the solubility of the main solvent in water is 100 g / 100 ml or more, the fiber diameter changes due to the change of the relative humidity. This is because a fiber assembly can be manufactured. From this result of FIG. 6 described above, it is apparent that the average fiber diameter can be made substantially the same if the relative humidity is maintained at ± 2% of the predetermined relative humidity. As is clear from the results of FIG. 6, the smaller the variation of the relative humidity, the more constant the influence of moisture, so that it is preferably within ± 1.5% of the predetermined relative humidity. More preferably, it is within ± 1%. In order to maintain the predetermined relative humidity in this way, for example, a gas conditioned using a commercially available temperature and humidity controller is supplied to the spinning space 5 with a constant air volume, or a gas pressurized to a constant pressure is supplied to the spinning space 5. This can be achieved by supplying a constant air volume.

  In FIG. 1, by using the spinning container 6, the spinning space 5 (that is, the space between the nozzle 2 and the collection body 3) is surrounded and made a closed space, and therefore ± 2% of the predetermined relative humidity. It is easy to carry out the electrospinning method while maintaining the relative humidity.

  In addition, as shown in FIG. 1, it is preferable to supply a gas having a predetermined relative humidity to the spinning container 6 with a constant air volume. This is because if there is a change in the air volume, a difference occurs in the volatilization rate of the main solvent due to the change in the air volume, and as a result, there is a tendency to form a fiber assembly with a large variation in fiber diameter. This “constant air flow” means that the change in the air flow is within ± 10%. The smaller the air flow change, the smaller the fiber diameter variation, and thus the change in the air flow. Is preferably within ± 8%, more preferably within ± 5%. Examples of a method that can supply a gas having a predetermined airflow with a predetermined relative humidity include a method of supplying through a flow meter and a method of supplying compressed air decompressed to a constant pressure. In addition, the supply location of the gas of predetermined relative humidity does not need to be one place, and can supply from two or more places. Further, when there are a plurality of nozzles, they can be supplied for each nozzle.

  The gas supply direction of the predetermined relative humidity is not particularly limited as long as the relative humidity in the spinning space 5 can be maintained at the predetermined relative humidity. However, as shown in FIG. If the gas is supplied so that the relative humidity gas is supplied in the same direction, the flying of the fibers is not hindered. In FIG. 1, the nozzle 2 may be supplied from above to below, and conversely, the nozzle 2 may be supplied from below to above.

  Further, the supply amount of the gas having a predetermined relative humidity can be appropriately determined depending on the amount of the spinning dope to be extruded and the resin concentration. That is, the amount of solvent to be evaporated may be calculated, and the amount of gas larger than the amount of gas reaching the saturated vapor may be used as the supply amount. In addition, although there is no restriction | limiting in particular in the kind of gas of the predetermined relative humidity to supply, For example, air, nitrogen, a carbon dioxide, argon etc. can be used. Air is preferred from an economic standpoint.

  As the gas supply device 7, for example, a propeller fan, a sirocco fan, an air compressor, or a blower having a temperature / humidity adjustment function can be used.

  When the closed space is formed by the spinning container 6 as shown in FIG. 1, the spinning container 6 is not particularly limited as long as it can accommodate the nozzle 2 and the collector 3.

  In FIG. 1, electrostatic spinning can be performed while the gas in the spinning container 6 is discharged using the exhaust device 8. This is because when the electrospinning is performed, the vapor concentration of the solvent in the spinning vessel 6 becomes higher, the evaporation of the solvent is suppressed, the fiber diameter becomes thinner, and the fiber diameter tends to vary. In the worst case, the vapor concentration of the solvent reaches saturation and it becomes difficult to perform electrospinning, but the vapor concentration of the solvent in the spinning space 5 is constant by discharging the gas, and the fiber diameter This is because a fiber assembly composed of fibers having a desired fiber diameter can be stably manufactured. In addition, although the exhaust apparatus 8 is not specifically limited, For example, it can be a fan installed in the exhaust port. As shown in FIG. 1, when a gas having a predetermined relative humidity is supplied to the spinning container 6 by the gas supply device 7, the same amount of gas as the supply amount can be discharged simply by providing an exhaust port. The device 8 is not necessarily provided. In addition, when exhausted by the exhaust device 8 as shown in FIG. 1, the exhaust amount is preferably the same as the supply amount. This is because when the supply amount and the exhaust amount are different, the pressure in the spinning space 5 is changed, whereby the evaporation rate of the solvent is changed and the fiber diameter is likely to vary.

  As described above, the manufacturing apparatus in FIG. 1 is an embodiment in which a closed space is formed by using the spinning container 6, but the present invention is not limited to an embodiment in which the spinning container 6 is used. As shown in the schematic schematic cross-sectional view of the fiber assembly manufacturing apparatus, a spinning container auxiliary member 6b capable of forming a gap between a partially opened spinning container body 6a and the opened portion of the spinning container body 6a. Can be combined to form a closed space and maintain the spinning space 5 at a predetermined relative humidity. The manufacturing apparatus in FIG. 2 uses a spinning container main body 6a and a spinning container auxiliary member 6b in place of the spinning container 6, arranges the position of the gas supply device 7 in a direction perpendicular to the flying direction of the fiber, Except for supplying a gas having a relative humidity and not providing the exhaust device 8, the manufacturing device of FIG. In FIG. 2, the spinning container auxiliary member 6b larger than the opening part of the spinning container body 6a is used. However, even if the spinning container auxiliary member 6b is the same size or smaller than the opening part of the spinning container body 6a, it is closed. Space can be formed. In FIG. 2, the position of the gas supply device 7 is set in a direction orthogonal to the flying direction of the fibers so that the gas can be easily exhausted from the exhaust port 8a formed by the spinning container main body 6a and the spinning container auxiliary member 6b. However, as long as the spinning space 5 can be maintained at a predetermined relative humidity, the gas supply device 7 may be disposed anywhere. Further, in FIG. 2, an exhaust port 8a is simply formed by the spinning vessel main body 6a and the spinning vessel auxiliary member 6b, but an exhaust device 8 is installed in the same manner as in FIG. 1, such as connecting a fan to the exhaust port 8a. You may do it.

  As described above, the manufacturing apparatus of FIG. 1 is an embodiment in which a closed space is formed by using the spinning vessel 6, but as long as the spinning space 5 can be maintained at a predetermined relative humidity, the manufacturing apparatus of FIG. It can also be implemented in an open state as shown in (cross section). That is, FIG. 3 does not include the spinning container 6 as shown in FIG. 1, and the spinning space 5 is maintained at the predetermined relative humidity by passing the gas having a predetermined relative humidity from the gas supply device 7 through the buffer box 9. The manufacturing apparatus in FIG. 3 does not include the spinning container 6, does not include the exhaust device 8, and except that the gas having a predetermined relative humidity from the gas supply device 7 passes through the buffer box 9, and FIG. It can be exactly the same. The buffer box 9 is for adjusting the air volume so that the air volume does not change locally, that is, so that the air volume in the spinning space 5 is constant. Or it can comprise from the box provided with porous materials, such as resin punching plates, cloth, and a nonwoven fabric.

  As described above, the manufacturing apparatus in FIG. 1 is a mode in which gas is simply supplied from the gas supply apparatus 7, but as in the manufacturing apparatus in FIG. 4, the porous material 10 a (for example, a metal or resin punching plate, Gas can be supplied through a cloth, a nonwoven fabric, etc.). That is, FIG. 4 includes the porous material 10a so that the supply amount of the gas supplied from the gas supply device 7 to the spinning space 5 can be made constant. The manufacturing apparatus in FIG. 4 has a gas supply direction from the gas supply apparatus 7 in a direction perpendicular to the discharge direction of the spinning dope, the porous material 10a as described above, and the same porosity as described above. Except that the luminescent material 10b is provided in front of the exhaust device 8, it can be exactly the same as in FIG. In addition, by providing the porous material 10b, exhaust does not occur locally, a uniform gas flow from the upper side to the lower side in the spinning vessel 6 can be formed, and the relative humidity and the air volume in the spinning space 5 can be reduced. Can be constant.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

(Example)
A spinning stock solution (viscosity: 930 mPa · s) was prepared by dissolving polyacrylonitrile having a weight average molecular weight of 420,000 in N, N-dimethylformamide so as to have a concentration of 10 mass%.

  A manufacturing apparatus as shown in FIG. 4 was prepared. That is, a polytetrafluoroethylene tube was connected to the syringe (spinning stock solution supply device 1), and a stainless steel nozzle 2 having an inner diameter of 0.4 mm was attached to the tip of the tube. Next, a high voltage power source (voltage application device 4) was connected to the nozzle 2. Furthermore, a drum (collector 3, grounded) having a stainless steel thin plate with conductive fluorine processing applied to the surface was installed at a position 10 cm away from the nozzle 2. The nozzle 2 and the drum 3 were placed in a transparent vinyl chloride rectangular parallelepiped spinning container 6 (width: 800 mm, height: 800 mm, depth: 650 mm). A gas supply device 7 was connected above the rectangular parallelepiped spinning vessel 6. This gas supply device 7 is composed of an air compressor, a hollow fiber membrane type dehumidifier, a flow meter with a valve and a bubbler. After passing the air of the air compressor through the hollow fiber membrane type dehumidifier, it is branched into two, each with a valve. Supplied to the flow meter, one air is bubbled (water bubbling air) in warm water, the other air (dehumidified air) is left as it is, and these airs are mixed again to adjust the humidity to the rectangular parallelepiped spinning vessel 6 Air can be supplied. Further, an exhaust fan (exhaust device 8) was connected to the lower side of the rectangular parallelepiped spinning container 6, and a humidity sensor was installed in front of the exhaust port to which the exhaust fan 8 of the rectangular parallelepiped spinning container 6 was connected. In addition, the rectangular parallelepiped spinning container 6 can make the supply amount of the gas supplied from the gas supply device 7 constant, and can make the relative humidity and the air volume in the spinning space 5 constant. Punching plate (porous material 10a) And a punching plate (porous material 10b).

  Next, the spinning solution is put into the syringe 1 and extruded using a microfeeder in a direction perpendicular to the action direction of gravity (extrusion amount: 2.5 g / hour), and the drum 3 is moved at a constant speed (surface speed: While rotating at 0.9 m / min), a voltage of +16 kV is applied from the high voltage power source 4 to the nozzle 2, and an electric field is applied to the extruded spinning stock solution to form a fiber, which is accumulated on the stainless steel thin plate of the drum 3. To form a fiber assembly. When forming the fiber assembly, by adjusting the flow rates of the dehumidifying air and bubbling air of the gas supply device 7, the humidity-controlled air set at a relative humidity of 30% is supplied at a rate of 200 L / min. Change rate: ± 1% or less), and the exhaust gas from the exhaust port is exhausted by the exhaust fan 8, and the relative humidity in the rectangular parallelepiped spinning container 6, that is, in the spinning space 5, is maintained at 29.3 to 31.5%. did. Further, when forming the fiber assembly, the nozzle 2 is reciprocally swung at a constant speed (moving speed: 2.5 cm / min) in a direction perpendicular to the rotation direction of the drum 3, thereby improving the uniformity of the fiber assembly. Increased.

  An electron micrograph was taken of both surfaces of the obtained fiber assembly, the fiber diameter (50 fibers) was measured from each electron micrograph, and the average fiber diameter was calculated. It was a fiber assembly having a uniform diameter.

(Comparative example)
In place of the gas supply device 7 of the embodiment, air was supplied at a rate of 200 L / min using a blower (rate of change in air volume: ± 5% or less) and the gas coming out from the exhaust port was exhausted by the exhaust fan 8 Except for the above, a fiber assembly was produced in the same manner as in the example. In addition, the relative humidity in the rectangular parallelepiped spinning container 6, that is, in the spinning space 5, was 28.8 to 37.5%, and the relative humidity fluctuated so as to be lower in the latter half.

  An electron micrograph was taken of both surfaces of the obtained fiber assembly, the fiber diameter (50 fibers) was measured from each electron micrograph, and the average fiber diameter was calculated, but one side was 0.40 μm. On the other hand, the other surface was 0.35 μm, and the fiber aggregate had a large variation in fiber diameter.

Conceptual schematic cross-sectional view of a fiber assembly manufacturing apparatus Conceptual schematic cross-sectional view of another fiber assembly manufacturing apparatus Conceptual schematic cross-sectional view of yet another fiber assembly manufacturing apparatus Conceptual schematic cross-sectional view of yet another fiber assembly manufacturing apparatus Conceptual schematic cross-sectional view of yet another fiber assembly manufacturing apparatus Graph showing the relationship between relative humidity and average fiber diameter

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Spinning stock solution supply apparatus 2 Nozzle 3 Collecting body 4 Voltage application apparatus 5 Spinning space 6 Spinning container 6a Spinning container main body 6b Spinning container auxiliary member 7 Gas supply apparatus 8 Exhaust apparatus 8a Exhaust port 9 Buffer box 10a Porous material 10b Porous material 11 Aluminum plate (collector)

Claims (3)

In a method of producing a fiber assembly by directly collecting fibers spun by an electrospinning method using a spinning stock solution in which a resin is dissolved in a solvent, the solubility in water as a solvent of the spinning stock solution is 100 g / 100 ml or more. And a method in which a spinning space by electrostatic spinning is maintained at a predetermined relative humidity of 40% or less and a relative humidity of ± 2% of the predetermined relative humidity. A method for producing a fiber assembly. The solvent as a main component of the spinning dope is a solvent selected from N, N-dimethylformamide, N, N-dimethylacetamide and N-methyl-2-pyrrolidone. A method for producing a fiber assembly. The closed space is formed so as to surround the spinning space by the electrostatic spinning method, and the gas having the predetermined relative humidity is supplied to the closed space with a constant air volume. The manufacturing method of the fiber assembly of description.

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