JP4938277B2 - Manufacturing method of fiber structure by electrostatic spinning method - Google Patents

Description

  The present invention relates to a method for manufacturing a fiber structure. More specifically, the present invention relates to a method for easily eliminating a manufacturing process abnormality that occurs unexpectedly and stably maintaining continuous production of a fiber structure in a method of manufacturing a fiber structure of a fiber-forming substance by an electrostatic spinning method. .

  As a technique for spinning various fiber-forming substances, a melt-formed fiber-forming substance is spun from a nozzle, and this is cooled and solidified in the air or in a certain gas to obtain fibers. ”Or“ dry spinning method ”in which a fiber-forming substance-containing solution is spun from a nozzle and the solvent component is evaporated therefrom to obtain fibers. Similarly, a fibrous fiber-forming substance spun from a nozzle is coagulated liquid. In general, a “wet spinning method” in which fibers are solidified to obtain fibers is known.

  In addition, the technology for producing fiber structures, particularly nonwoven fabrics, applies the above-described spinning technology. In addition to the “dry method” and “wet method”, a process of drawing and opening is performed after melt spinning. The “spunbond method” for obtaining a nonwoven fabric and the “meltblown method” for obtaining a nonwoven fabric by blowing and opening a fibrous fiber-forming substance by blowing a high-temperature and high-pressure air stream to the melt spinning nozzle port are generally known. ing.

  Various efforts have been made to use these spinning technology and fiber structure manufacturing technology to provide new characteristics not found in existing fibers and fiber structures. In particular, efforts are being made to impart new functions by minimizing the fiber diameter and improving the surface area per unit weight.

  However, the diameter of the fiber obtained by utilizing the above-described spinning technology and fiber structure manufacturing technology, and the diameter of the fiber constituting the fiber structure are the same diameter as existing fibers (several to several tens of μm). It is difficult to produce fibers with submicron or nanoscale diameters. In addition, facilities used for extruding a polymer compound under high pressure and cooling / solidifying a fibrous fiber-forming substance are complicated and expensive, which hinders an increase in manufacturing cost and stable product supply.

  Therefore, “electrostatic spinning method” which is also taken up in Patent Documents 1 and 2 is attracting attention as a new spinning technique. In this method, a fiber-forming substance-containing solution is charged to the positive electrode or the negative electrode, and the fibrous fiber-forming substance laminated portion charged to the opposite polarity or grounded is spun through a nozzle or a needle. It is a way to put out. The charged fibrous fiber-forming substance is thinned by an electric attractive force generated in an electrostatic field while reaching the laminated portion. According to this method, a fiber having a diameter of several nm can be produced.

  On the other hand, studies on mass production technology, which is the subject of this method, are also being actively conducted. In Patent Document 3, a barrel that stores a liquid polymer material, a pump that pressurizes the liquid polymer material from the barrel, and a spinning device that injects the liquid polymer material supplied from the pump through a charged nozzle. A polymer web manufacturing apparatus is taught which includes a web laminating unit (collector) charged with a polarity different from that of a spinning unit, a high voltage generating unit for charging a liquid polymer substance, and a spinning unit. According to this method, it is possible to produce a polymer web at high speed and in large quantities, unlike laboratory-scale production using a single needle provided for research purposes.

  In addition, Patent Document 4 teaches a similar mass production method. This method comprises a step of producing a polymer solution, a step of spinning the polymer solution by a charge-induced spinning method, and a step of obtaining a polymer web on the web laminate, and the relative humidity of the spinning step and the polymer solution By controlling the temperature, it is possible to mass-produce a polymer web having a desired fiber diameter.

  However, in these methods, the spinning process and the process for obtaining the polymer web are only one series, and when an abnormality occurs in the manufacturing process, it is necessary to stop the operation in all the processes. give. Further, when all the processes are stopped or started up, each process is not stable, and a polymer web having a uniform structure cannot be obtained continuously, so that quality control of the obtained product becomes extremely difficult.

  When the electrospinning method is used, the amount of spinning is very small, so the solvent volatilization rate is high during spinning, and manufacturing process abnormalities such as cylinder and needle clogging due to solidification of the fiber-forming substance are likely to occur. . While studies on mass production technology are becoming popular, studies on countermeasures against such manufacturing process anomalies have not progressed at all.

US Pat. No. 6,106,913 US Pat. No. 6,110,590 JP 2002-201559 A JP 2002-249966 A

  Even when manufacturing process abnormalities such as those described above occur, it is necessary to efficiently eliminate these problems and to study a technique for continuously and stably manufacturing a fiber structure having a uniform structure. . Accordingly, an object of the present invention is to easily eliminate a manufacturing process abnormality that occurs unexpectedly in a method for producing a fiber structure of a fiber-forming substance by an electrospinning method, and stably maintain continuous production of the fiber structure. It is to provide a method of making it happen.

The inventors diligently studied in order to solve the above-described problems and arrived at the following invention.
1. In the method for producing a fiber structure by an electrostatic spinning method, a plurality of spinning sections (A) for spinning the fiber-forming substance-containing solution (B) charged to the positive electrode or the negative electrode are arranged so as to be switchable. At least one part of the spinning section (A ′) is put under operation, and the other spinning section (A ″) not subjected to the operation is subjected to a regeneration operation for regenerating the spinning section (A ″). A method for producing a fiber structure, characterized in that the flow rate of the solution (B) supplied to the spinning section (A ″) under regeneration operation is set to the spinning section under operation. Increasing the flow rate of the solution (B) supplied to (A ′) and allowing the solution (B) to flow until the spinning section (A ″) is placed in the next operation, or The tip of the spinning nozzle provided in the spinning section (A ″) under the regeneration operation is connected to the spinning section. A ") is kept immersed in the solution (B) to be placed under the following operating method of the fiber structure.
2. 2. The production method according to 1 above, wherein the discharged solution (B) is supplied again to the spinning section (A ″) and recycled for discharging the solution (B).
3. By adding the same solvent as the solvent (C) contained in the solution (B) to the spinning section (A ″) under the regeneration operation and further pressurizing with an inert gas, the spinning section ( 2. The production method according to 1 above, wherein the solution (D) after addition of the solvent (C) remaining in A ″) is removed.
4). The added amount of solvent (C) is removed from the solution (D) removed from the spinning section (A ″), and the resulting solution (B) is circulated in the production for obtaining the fibrous structure. The manufacturing method according to 3 above, which is reused.
5. The additional solvent (C) removed from the solution (D) removed from the spinning section (A ″) is recycled and reused to remove the solution (D) from the spinning section (A ″). 3. above. Or 4. The manufacturing method as described in.
6). 6. The production method according to 1 to 5 above, wherein the spinning part (A ″) under the regeneration operation is heated at a temperature not higher than the boiling point of the solvent (C).

  By using the above-described method for producing a fiber structure by an electrostatic spinning method, the spinning nozzle tip provided in the spinning part (A ″) has a fiber forming property contained in the solution (B). Since it is not solidified by the substance, continuous and stable production of a fiber structure having a uniform structure can be realized over a long period of time, and the number of production process abnormalities that occur unexpectedly is reduced, resulting in a defective product rate. In addition to an increase in manufacturing cost due to the increase, an increase in maintenance cost can be suppressed, and economical manufacturing can be performed.

The production method of the present invention will be described in detail below.
In the following, as representative steps of the present invention,
(1) A solution storage unit for preparing a fiber-forming substance-containing solution and storing the solution (2) A spinning unit (A) that applies high voltage to the solution and performs electrostatic spinning
(3) A heating unit for drying and / or firing the resulting fiber structure and / or substrate. (4) Explaining the present invention in detail by exemplifying a process comprising each part of a product recovery unit for recovering the obtained fiber structure. As will be described, the scope of the present invention is not particularly limited thereby.

  In the storage part (1) for preparing a fiber-forming substance-containing solution and storing the solution, first, the fiber-forming substance and the solvent are put into the solution storage tank, and mixed and stirred. In order to prepare a uniformly dissolved solution, the solution may be mechanically stirred and the storage tank may be heated in parallel with the operation, but is not particularly limited thereto.

  Examples of the fiber-forming substance used in the present invention include polypropylene, polyethylene, polystyrene, polyethylene oxide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, poly-m-phenylene terephthalate, poly-p-phenylene isophthalate, polyfluoride. Vinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl chloride, polyvinylidene chloride-acrylate copolymer, polyacrylonitrile, polyacrylonitrile-methacrylate copolymer, polycarbonate, polyarylate, polyester carbonate, nylon, aramid, Examples include polycaprolactone, polylactic acid, polyglycolic acid, collagen, polyhydroxybutyric acid, polyvinyl acetate, and polypeptide Can, at least one selected from these are used, but the invention is not particularly limited thereto.

  Examples of the solvent used in the present invention include methanol, ethanol, 1-propanol, 2-propanol, hexafluoroisopropanol, tetraethylene glycol, triethylene glycol, dibenzyl alcohol, 1,3-dioxolane, 1,4-dioxane, Methyl ethyl ketone, methyl isobutyl ketone, methyl n-hexyl ketone, methyl n-propyl ketone, diisopropyl ketone, diisobutyl ketone, acetone, hexafluoroacetone, phenol, formic acid, methyl formate, ethyl formate, propyl formate, methyl benzoate, benzoic acid Ethyl acetate, propyl benzoate, methyl acetate, ethyl acetate, propyl acetate, dimethyl phthalate, diethyl phthalate, dipropyl phthalate, methyl chloride, ethyl chloride, methylene chloride, chloroform , O-chlorotoluene, p-chlorotoluene, chloroform, carbon tetrachloride, 1,1-dichloroethane, 1,2-dichloroethane, trichloroethane, dichloropropane, dibromoethane, dibromopropane, methyl bromide, ethyl bromide, bromide Examples include propyl, acetic acid, benzene, toluene, hexane, cyclohexane, cyclohexanone, cyclopentane, o-xylene, p-xylene, m-xylene, acetonitrile, tetrahydrofuran, N, N-dimethylformamide, pyridine, water, and the like. At least one selected from these is used, but is not particularly limited thereto.

It is also possible to mix an inorganic solid material in the fiber-forming substance and the solvent described above. Examples of the inorganic solid material include oxides, carbides, nitrides, borides, silicides, fluorides, sulfides, etc., but oxides are preferably used from the viewpoint of heat resistance and workability. .
Examples of the oxide include Al ₂ O ₃ , SiO ₂ , TiO ₂ , Li ₂ O, Na ₂ O, MgO, CaO, SrO, BaO, B ₂ O ₃ , P ₂ O ₅ , SnO ₂ , ZrO ₂ , K. _{2 O, Cs 2 O, ZnO} , Sb 2 O 3, As 2 O 3, CeO 2, V 2 O 5, Cr 2 O 3, MnO, Fe 2 O 3, CoO, NiO, Y 2 O 3, Lu 2 O ₃ , Yb ₂ O ₃ , HfO ₂ , Nb ₂ O _{5 and the} like can be exemplified, and at least one selected from these can be used, but is not particularly limited thereto.

Next, the prepared solution described above is fed to the spinning section (A) (2) that performs electrostatic spinning by applying a high voltage to the solution via a feeding pipe.
The spinning section (A) includes a spinning nozzle that spins the solution, a high voltage generator that applies a high voltage to the nozzle, a charging electrode that is inserted into the nozzle, and a charge polarity opposite to that of the solution. It is composed of a counter electrode charged in polarity or grounded, a base material moving between the nozzle and the counter electrode, an unwinding roll and a free roll for unwinding and transporting the base material.

  In addition, the base material already described can also be used for the purpose of transferring the obtained fiber structure, or can be used as a product together with the fiber structure. In the case of the former, as a base material to be used, a plain structure, a twill weave, a flat tatami weave, etc., a mesh structure such as a wire mesh, a punched wire mesh, a perforated plate, a metallic flat plate, A belt-like structure etc. can be illustrated. In the latter case, polypropylene, polyethylene, polystyrene, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyvinyl chloride, polyacrylonitrile, polycarbonate, polyarylate, polyester carbonate, nylon, aramid, polycaprolactone, polylactic acid, General-purpose nonwoven fabrics and felts made of industrial resins such as polyglycolic acid can be exemplified, but both are not particularly limited to these.

  In the spinning section (A), a high voltage is applied to the fiber-forming substance-containing solution fed to the spinning nozzle via a high-voltage and high-voltage generator and a charging electrode. Since an electric attractive force is generated along with the formation of an electrostatic field between the nozzle and the counter electrode charged to the opposite polarity to the solution charged by the nozzle or grounded, the solution is discharged from the nozzle. Spinning, and the electric attractive force promotes thinning of the spun fiber. Since the base material continuously moves between the nozzle and the counter electrode, a fiber structure made of the spun fibers is laminated on the base material, and this is transferred to the next step.

  Thereafter, in the heating unit (3) for drying and / or firing the obtained fiber structure and / or substrate, the solvent contained in a trace amount in the fiber structure and / or substrate is removed by heating. It is transferred to the process. Moreover, when manufacturing the fiber structure containing an inorganic type solid material, the said part (3) may be used for the objective of baking other than the objective of drying.

  The fiber structure thus obtained is recovered by a product recovery unit (4) that recovers the obtained fiber structure. As described above, when the base material on which the fiber structure is laminated is handled as a product, the base material is collected together with the fiber structure and processed into a shape according to the purpose and used. When the base material is simply used for transferring the fiber structure, an operation of peeling the base material and the fiber structure at the portion (4) is also added.

By the steps described above, a desired fiber structure can be obtained as a product, but the diameter of the fiber obtained by the electrospinning method is about several nm to 1 μm as described above, and from the nozzle described above The amount of the fiber-forming substance-containing solution to be spun is extremely small as compared with the conventional spinning method. Moreover, since the solution of such a micro flow rate is handled, the nozzle outlet diameter of the nozzle is also extremely small.
Therefore, according to this method, the retention of the solution due to a small amount of spinning and the blockage of the spinning port due to the minimum nozzle outlet diameter occur more frequently than in the conventional spinning method. To do.

  In addition, as described above, since the amount of the solution spun from one nozzle outlet of the nozzle is very small, a spinning nozzle having a plurality of nozzles is provided to improve the production efficiency of the fiber structure. In many cases, a spinning section (A) having a plurality of stages is employed. However, if the aforementioned spinning outlets are frequently blocked during production, spots will occur in the lamination of the fiber structure to the base material, so that a fiber structure having the desired uniform properties cannot be obtained. .

  Further, when the nozzle is clogged at the nozzle outlet, an excessive back pressure is applied to the nozzle, and there is a risk of damage to the nozzle and the parts constituting the upper reservoir (1). This not only increases the cost associated with the restoration and maintenance of damaged parts, but in the worst case, there is a risk that the worker who performs the manufacturing will encounter a disaster.

  Therefore, in the production method of the present invention, a plurality of spinning parts (A) for spinning the fiber-forming substance-containing solution (B) charged to the positive electrode or the negative electrode are arranged so as to be switchable, and at least one part of the relevant part is provided. The spinning section (A ′) is put under operation, and the other spinning section (A ″) not subjected to the operation is subjected to a regeneration operation for regenerating the spinning section (A ″).

  According to this method, for example, when the spinning nozzle of the spinning nozzle (A) disposed in the spinning section (A) is closed, the rising back pressure is sensed, and the defective spinning section (A ″) is immediately put under a regeneration operation. In the meantime, since the good spinning section (A ′) can be put under operation, it is possible to minimize trouble caused by the nozzle spout clogging. When a failure occurs, the spinning section (A ″) placed under the regeneration operation can be used again as the spinning section (A ′) at the same time as the spinning section.

  According to the above method, the spinning section (A) is switched by detecting the nozzle spout blockage with the rising back pressure. In addition, the spinning section (A A method of observing A) and performing the switching operation as described above when a defect occurs in the nozzle, a method of performing the switching operation as described above regularly regardless of whether an abnormality has occurred, or the like can be exemplified. .

By using the above method, continuous and stable production of a fiber structure having a uniform structure can be realized over a long period of time. However, in order to perform the production economically, the spinning nozzle that becomes defective due to the clogging of the spinning outlet must be regenerated for the next operation. If the spinning nozzle that has become defective is left as it is, the problem of blockage of the spout will also occur, and some measure is also required for the regeneration operation.
Therefore, in the present invention, the flow rate of the solution (B) supplied to the spinning section (A ″) under the regeneration operation is increased, and the solution (B) until the spinning section (A ″) is placed under the next operation. B) is released.

The blockage at the spinning outlet of the spinning nozzle described above is that the solution (B) stays in the vicinity of the spinning outlet, the contained solvent volatilizes during that time, and the concentration of the fiber-forming substance in the solution increases. Caused by. Therefore, if the solution (B) is not retained in the vicinity of the spinning outlet and placed in a constantly flowing state, the above-described problems are solved.
However, the flow rate of the solution (B) discharged in the spinning section (A ″) placed under the regeneration operation is the same as the amount of liquid fed to the spinning section (A ′) placed under the operation, or In the case of a small amount, the fluid (B) is less fluid in the former because the electric attractive force due to the electrostatic field does not work. If the state in which the fluidity of the solution (B) is poorer than is maintained, the risk of further clogging of the spinning outlet increases.

According to this method, the solution (B) is discharged from the spinning outlet of the spinning nozzle of the spinning section (A ″) placed in the regeneration operation, and the spinning section (A ″) is placed in the next operation. In order to carry out until it is removed, the solution (A ′) near the spinning outlet of the spinning nozzle of the spinning section (A ″) placed in the regeneration operation is compared with the solution ( Since the fluidity of B) is good, the solution (B) does not stay in the vicinity of the spinning outlet, and the spinning outlet is not blocked due to solidification of the solution (B).
In addition, it is also preferable that the discharged solution (B) is supplied again to the spinning section (A ″) and recycled for discharging the solution (B).

  According to the method described above, the amount of the solution (B) consumed by the spinning section (A ″) placed under the regeneration operation is larger than the spinning section (A ′) placed under the operation. When the amount of the solution (B) that does not directly affect the product increases and is discarded, the amount of the solution (B) used to produce the product per unit amount increases. The cost associated with disposal also adds to the cost of manufacturing the product, which makes it impossible to economically manufacture the fiber structure, which is another object of the present invention.

According to this method, since the discharged solution (B) is supplied again to the spinning section (A ″) and recycled for discharging the solution (B), a small amount of loss occurs in the circulation step. Since the stable production can be maintained only by replenishing only the amount, and no waste is generated, the above-described fibrous structure can be economically produced.
Furthermore, in the present invention, as a preferred method for the regeneration operation of the spinning section (A ″) described above, the solvent (C) contained in the solution (B) is contained in the spinning section (A ″) under the regeneration operation. It is also possible to employ a method of removing the solution (D) remaining in the spinning section (A ″) by adding the same solvent as (1) and pressurizing with an inert gas.

  As described above, the blockage in the vicinity of the spinning outlet of the spinning nozzle is caused by retention of the solution (B) at the site, that is, fluidity of the solution (B). By using the above-described method for always discharging the solution (B), problems relating to the retention and fluidity of the solution (B) can be solved, but the fiber-forming substance or solvent ( Depending on the properties of C), the specifications of the spinning nozzle, etc., the fluidity of the solution (B) may not be sufficiently ensured even by the method described above.

On the other hand, according to the present method, the same solvent as the solvent (C) contained in the solution (B) is added to the spinning section (A ″) under the regeneration operation, so that the solvent (C) fiber-forming substance containing a concentration of solvent solution sod after hydrogenation (D) is greatly reduced as compared with the original, also viscosity also decreases. Therefore fluidity of the solution (D) in the spinning unit (a ") in Is significantly improved compared to the original, so that the spinning port is not easily blocked as described above.

Therefore, like the method described above, the same solvent as the solvent (C) contained in the solution (B) is added to the spinning section (A ″) under the regeneration operation, and the solvent (C ) If the solution (D) after the addition is discharged, the problem of the clogging of the spinning outlet can be solved, but if the problem is solved by discharging the solution (D), the spinning section (A ″) ) Is filled with the solution (D) that is different from the properties of the fiber-forming substance-containing solution (B) used in the production, so that the solution (D) is placed before the spinning section (A ″) is placed under the next operation. In order to do this, it is necessary to remove the solution (D) from the spinning section (A ″). It is necessary to shorten the time required for the switching of the part (A ") and the regenerative operation as much as possible. In the sense of reducing, the method needs to be simplified as much as possible.
Therefore, in this method, as a method of removing the solution (D) from the spinning section (A ″), an inert gas is used, and thereby the solution (D) is pressurized to remove the solution (D). Do.

According to this method, the solution (D) can be quickly removed from the spinning section (A ″) by a simple method of pressurizing the solution (D) with an inert gas. In addition, an inert gas is used. Therefore, the solution (D) and the gas cause an abnormal reaction, and the solution is not denatured.
In addition, as such an inert gas, air, nitrogen, carbon dioxide, helium, argon, etc. can be illustrated as suitable gas, However, The most preferable gas is nitrogen.

  Furthermore, in the present invention, the added amount of solvent (C) is removed from the solution (D) removed from the spinning section (A ″), and the resulting solution (B) is obtained as the fiber structure. It is also preferable to recycle in production.

  As the regeneration operation method for the spinning section (A ″), the method for discharging the solution (B) has been described. However, in this method, the spinning section (A ′) placed under operation is placed under the regeneration operation. There is a problem that the amount of the solvent (C) consumed in the spinning section (A ″) is increased. If the amount of the solvent (C) that does not directly affect the product increases and is discarded, the amount of the solvent (C) used to produce the product per unit amount increases, Since the cost for disposal is also added, the manufacturing cost of the product is greatly increased. This makes it impossible to economically manufacture the fiber structure, which is another object of the present invention.

  According to this method, the added amount of solvent (C) is removed from the solution (D) removed from the spinning section (A ″), and the resulting solution (B) is removed from the fiber structure. Since the solution (B) is commercialized without waste because it is recycled and reused in the production process for obtaining, it is possible to economically produce the fiber structure described above.

Further, in the present invention, the additional solvent (C) removed from the solution (D) removed from the spinning part (A ″) is removed from the spinning part (A ″) by removing the solution (D). It is also preferable to be characterized by recycling.
The above method is also a measure that enables economical production. According to this method, the additional solvent (C) removed by the above-described method is supplied from the spinning section (A ″) to the solution. In order to recycle and reuse (D), the amount of the solvent (C) used may be supplemented with only a small amount of loss in the circulation step of the solvent (C) and discarded. Since the solvent can also be reduced, the above-described fibrous structure can be produced economically.

  Further, in the present invention, as a preferable method for the regeneration operation of the spinning section (A ″) described above, the tip of the spinning nozzle provided in the spinning section (A ″) under the regeneration operation is connected to the spinning section ( It is also possible to employ a method of immersing in the solution (B) until A ″) is placed under the next operation.

  As described above, clogging occurs near the spinning outlet due to the low fluidity of the solution (B) near the spinning outlet of the spinning nozzle. This is because the solution (B) near the spinning outlet is closed. This is also caused by the extremely narrow flow path. When the flow path in which the solution (B) stays is extremely narrow, since the ratio of the solution (B) in the space volume of the flow path is very high, the contained solvent (B) volatilizes and the solution (B When the solidification of the fiber-forming substance in B) starts, the solidified material will occupy most of the space volume, resulting in blockage of the spinning outlet. Therefore, if importance is attached to the narrowness of the flow path described above rather than emphasizing the fluidity of the solution (B), an especially large amount of the solvent (B ), It is possible to avoid the problems related to the blockage described above.

  Therefore, according to the present method, the tip of the spinning nozzle provided in the spinning section (A ″) under the regeneration operation is kept until the spinning section (A ″) is placed under the next operation. Since the spinning outlet is not blocked, the switching operation for placing the spinning port under the next operation can be performed quickly.

In the regeneration operation described in detail so far, heating the spinning section (A ″) at a temperature not higher than the boiling point of the solvent (C) is also a preferred method in the present invention.
This is because when the spinning section (A ″) is heated, the viscosity of the solution (D) to which the solution (B) or the solvent (C) is added decreases, and the spinning section (A ″) This is because the fluidity of these solutions is improved, and it is more effective in regenerating the spinning section (A ″) and shortening the switching time than the regenerating operation method described in detail so far.

  In addition, these solutions used in the regeneration operation are reused for product production and regeneration operation again, and further, the additional amount of supplementing these solutions lost in the process at that time is reduced. An operation that greatly changes the composition should be avoided. In order to suppress volatilization of the solvent (C), it is preferable that the heating temperature described above is equal to or lower than the boiling point of the solvent (C).

Furthermore, in the present invention, the tip of the spinning nozzle provided in the spinning section (A ″) is immersed in the solution (B) until the spinning section (A ″) is placed in the next operation. In this method, it is also preferable to use the solvent (C) in place of the solution (B).
According to this method, the tip of the spinning nozzle provided in the spinning section (A ″) is immersed in the solution (B) until the spinning section (A ″) is placed in the next operation. In addition to being able to reproduce the advantages of the method described above, even if clogging occurs at the spinning nozzle tip of the spinning nozzle, the solidified product dissolves in the solvent (B). It can be maintained until the spinning section (A ″) is placed under the next operation.

  As described above, by using the production method detailed above, particularly the regeneration method of the spinning section (A ″), even when a production process abnormality such as a spinning port blockage occurs, these can be solved efficiently and evenly. It is possible to manufacture a fiber structure with a structure continuously and stably, and because the manufacturing process abnormality itself is reduced, it is also effective in reducing costs required for recovery and maintenance. It also enables economical product manufacture, which is another object of the present invention.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto.
[Example 1]
A series of three Teflon (registered trademark) spinning nozzles (general dimensions: W210 × L60 × H40 mm, number of spinning ports: 6) for one Teflon (registered trademark) solution storage tank (internal volume: 1000 mL) Were prepared in series (each referred to as A ′ series and A ″ series). These series were arranged in parallel, so that these series could be exchanged with each other by remote control.

  Further, a high voltage generator for applying a high voltage to the prepared solution, a counter electrode, an unwinding roll for transferring the substrate, a free roll, and a heating furnace for heating and drying the resulting fiber structure, and obtained A set of all the take-up rolls for collecting the product was prepared, and the structure was such that the series of the spinning nozzles described above could be switched on the substrate to be transferred.

  Prior to the production operation of the product, the roll-shaped substrate was attached to the unwinding roll, and manually led to the free roll and then to the winding roll. In order to collect the base material as a product, a polyester nonwoven fabric was used as the base material here. 400 mL of a 10 wt% mixed solution of polyacrylonitrile and N, N-dimethylformamide prepared in advance was charged into the A ′ series solution storage tank. 800 mL of the same prepared solution was put into the A ″ series solution storage tank.

  Subsequently, the manufacturing operation of the fiber structure using A 'series was started. The applied voltage at this time was 15 kV, the distance between the spinning nozzle tip and the substrate was 140 mm, and the substrate transfer speed was 0.1 m / min. During the manufacturing operation, the vicinity of the spinning nozzle was constantly monitored using a CCD camera. Furthermore, apart from the manufacturing operation, the A ″ series started to discharge the prepared solution. Since the amount of the prepared solution stored in the A ′ series solution storage tank and the A ″ series solution storage tank differ, In the A ″ series, the solution was discharged at a larger flow rate than the A ′ series.

  128 minutes after starting the production operation in the A ′ series and the regeneration operation in the A ″ series, the spinning of the preparation solution is defective at a part of the spinning nozzle outlet of the A ′ series. Therefore, in order to place the A ″ series under operation and the A ′ series under regeneration operation, these series were immediately switched. The operating conditions of the A ″ series after the switching were the same as the operating conditions of the A ′ series before the switching. In addition, the A ′ series of solution storage tanks placed under the regeneration operation were regenerated before the switching. The discharged adjustment solution was collected and charged, and the adjustment solution was discharged as described above.

  Before and after the switching, the pressure applied to the head of the stored preparation solution was reversed, so that the solution was discharged at a flow rate higher than that of the A ″ series in the A ′ series. Similarly, after continuing for 128 minutes, the series was switched again, and the A ′ series was put into operation and the A ″ series was put into a regeneration operation.

  After continuing the operation for 60 minutes in this state, all production was completed. The finally obtained fiber structure was collected from a take-up roll, and the presence or absence of planar stacking spots of the fiber structure was visually confirmed. Moreover, the said fiber structure was peeled from the base material, 1 cm each fiber structure was cut out from arbitrary 20 places, and all these thicknesses were measured with the offline film thickness meter. Furthermore, all these surface states were observed with a scanning electron microscope. As a result, even during the production operation and when the switching operation was performed, no planar stacking spots of the fiber structure were confirmed. The thickness at each measurement location was all within ± 2.0 μm with respect to the average thickness of the fiber structure: 41 μm. Furthermore, the average value of the fiber diameters at each measurement point was within ± 30 nm with respect to the average value of the fiber diameters at all the measurement points: 310 nm.

[Example 2]
As a regeneration method of the series placed under the regeneration operation, a method is adopted in which N, N-dimethylformamide is added to the spinning nozzle and removed by pressurizing with nitrogen gas having a gauge pressure of 0.2 MPa. The procedure was the same as in Example 1 except that the time from the start of operation to the first series switching was 90 minutes, and thereafter the series switching was performed every 90 minutes.

As a result, even during the production operation and when the switching operation was performed, no planar stacking spots of the fiber structure were confirmed. The thickness at each measurement location was all within ± 2.0 μm with respect to the average thickness of the fiber structure: 37 μm.
Furthermore, the average value of the fiber diameters at each measurement point was within ± 30 nm for the average value of the fiber diameters at all the measurement points: 302 nm.

[Example 3]
As a regeneration method of the series placed under the regeneration operation, N, N-dimethylformamide was added to the spinning nozzle, and this was removed by pressurizing with nitrogen gas having a gauge pressure of 0.2 MPa, and the recovered removal solution Was flushed, and the added N, N-dimethylformamide was recovered and used in the same manner as in Example 2 except that it was used again as a solvent for addition to the spinning nozzle.

  As a result, even during the production operation and when the switching operation was performed, no planar stacking spots of the fiber structure were confirmed. The thickness at each measurement location was all within ± 2.0 μm with respect to the average thickness of the fiber structure: 35 μm. Furthermore, the average value of the fiber diameters at each measurement location was all within ± 30 nm with respect to the average value of the fiber diameters at all measurement locations: 322 nm.

[Example 4]
As a regeneration method of the series placed under regeneration operation, 2.1 L of a separately prepared 10 wt% mixed solution of polyacrylonitrile-N, N-dimethylformamide was distributed evenly to 3 stainless steel bats (internal volume: 800 mL), All operations were performed in the same manner as in Example 1 except that a method was adopted in which the spinning outlet at the tip of each spinning nozzle was allowed to stand in the prepared solution stored in the vat during regeneration.

  As a result, even during the production operation and when the switching operation was performed, no planar stacking spots of the fiber structure were confirmed. The thickness at each measurement location was all within ± 2.5 μm with respect to the average thickness of the fiber structure: 39 μm. Furthermore, the average value of the fiber diameter in each measurement location was all within ± 30 nm with respect to the average value of the fiber diameter in all measurement locations: 291 nm.

[Example 5]
The same procedure as in Example 2 was performed except that the spinning nozzle under the regeneration operation was heated. As a result, even during the production operation and when the switching operation was performed, no planar stacking spots of the fiber structure were confirmed. The thickness at each measurement location was all within ± 2.5 μm with respect to the average thickness of the fiber structure: 37 μm. Furthermore, the average value of the fiber diameter in each measurement location was all within ± 30 nm with respect to the average fiber diameter of all measurement locations: 311 nm.

[Example 6]
All were carried out in the same manner as in Example 4 except that the spinning nozzle under the regeneration operation was heated. As a result, even during the production operation and when the switching operation was performed, no planar stacking spots of the fiber structure were confirmed.
The thickness at each measurement location was all within ± 2.0 μm with respect to the average thickness of the fiber structure: 33 μm. Furthermore, the average value of the fiber diameter in each measurement location was all within ± 30 nm with respect to the average value of the fiber diameter in all measurement locations: 283 nm.

[Example 7]
As a regeneration method of the series placed under regeneration operation, 1.8 L of N, N-dimethylformamide is equally distributed to 3 pieces of stainless steel bats (internal volume: 800 mL), and the spout at the tip of each spinning nozzle during regeneration. Was carried out in the same manner as in Example 4 except that a method of leaving the solution in the solvent stored in the vat was adopted.

  As a result, even during the production operation and when the switching operation was performed, no planar stacking spots of the fiber structure were confirmed. The thickness at each measurement location was all within ± 2.0 μm with respect to the average thickness of the fiber structure: 28 μm. Furthermore, the average value of the fiber diameter in each measurement location was all within ± 25 nm with respect to the average value of the fiber diameter in all measurement locations: 278 nm.

[Comparative Example 1]
The preparation solution to be used, the base material, and the operating conditions were the same as those in Example 1, and the production operation was carried out only in the A ′ series without performing the series switching work. 155 minutes after the start of the production operation, a portion where spinning of the prepared solution was defective was confirmed at a part of the spinning nozzle spinning outlet.
Further, the production operation was continued in this state, and the production was completed after 300 minutes. The fiber structure finally obtained was collected from a take-up roll, and the presence or absence of planar stacking spots on the fiber structure was visually confirmed. In particular, the spinning of the prepared solution was performed at a part of the spinning nozzle spinning outlet. It was confirmed that marked stacking spots were generated from the time when the defect became defective.

[Comparative Example 2]
The sequence switching operation was performed with a switching interval of 90 minutes, but all operations were performed in the same manner as in Example 1 except that the regeneration processing of the spinning nozzle placed under the regeneration operation was not performed.
As a result, the lamination of the fiber structure to the base material was not confirmed after the second switching from the start of the production operation. When the spinning outlets of all spinning nozzles were confirmed with a CCD camera, gel-like obstructions were confirmed at all points.

Claims (6)

  In the method for producing a fiber structure by an electrostatic spinning method, a plurality of spinning sections (A) for spinning the fiber-forming substance-containing solution (B) charged to the positive electrode or the negative electrode are arranged so as to be switchable. At least one part of the spinning section (A ′) is put under operation, and the other spinning section (A ″) not subjected to the operation is subjected to a regeneration operation for regenerating the spinning section (A ″). A method for producing a fiber structure, characterized in that the flow rate of the solution (B) supplied to the spinning section (A ″) under regeneration operation is set to the spinning section under operation. Increasing the flow rate of the solution (B) supplied to (A ′) and allowing the solution (B) to flow until the spinning section (A ″) is placed in the next operation, or The spinning nozzle tip provided in the spinning section (A ″) under the regeneration operation is connected to the spinning machine. (A ") is kept immersed in the solution (B) to be placed under the following operating method of the fiber structure.   The production method according to claim 1, wherein the discharged solution (B) is supplied again to the spinning section (A ") and recycled for discharging the solution (B).   By adding the same solvent as the solvent (C) contained in the solution (B) to the spinning section (A ″) under the regeneration operation and further pressurizing with an inert gas, the spinning section ( The manufacturing method according to claim 1, wherein the solution (D) after the addition of the solvent (C) remaining in A ″) is removed.   The added amount of solvent (C) is removed from the solution (D) removed from the spinning section (A ″), and the resulting solution (B) is circulated in the production for obtaining the fibrous structure. The manufacturing method according to claim 3, which is reused.   The additional solvent (C) removed from the solution (D) removed from the spinning section (A ″) is recycled and reused to remove the solution (D) from the spinning section (A ″). The manufacturing method of Claim 3 or 4.   The production method according to any one of claims 1 to 5, wherein the spinning section (A ") under the regeneration operation is heated at a temperature not higher than the boiling point of the solvent (C).