阅读说明：本技术 无纺布制造方法及设备 (Method and apparatus for producing nonwoven fabric ) 是由 谷口幸助 于 2019-07-12 设计创作，主要内容包括：本发明提供一种提高从集电极的剥离性且更长时间连续制造无纺布的无纺布制造方法及设备。使充电带(13)沿长边方向移动并通过第1层形成工序、第2层形成工序及剥离工序来制造无纺布(11)。第1层形成工序中,使第1溶液(16)带电以形成第1层(11a)。第2层形成工序中,使第2溶液(17)带电以形成第2层(11b)。剥离工序中,从充电带(13)剥离具备第1层(11a)和第2层(11b)的无纺布(11)。第1溶液(16)与第2溶液(17)相比,聚合物的浓度更高。(The invention provides a method and equipment for manufacturing non-woven fabric, which can improve the stripping property from a collecting electrode and continuously manufacture the non-woven fabric for a longer time. A non-woven fabric (11) is produced by passing a charging belt (13) through a 1 st layer forming step, a 2 nd layer forming step and a peeling step while moving the belt in the longitudinal direction. In the 1 st layer forming step, the 1 st solution (16) is charged to form a 1 st layer (11 a). In the 2 nd layer forming step, the 2 nd solution (17) is charged to form the 2 nd layer (11 b). In the peeling step, the nonwoven fabric (11) having the 1 st layer (11a) and the 2 nd layer (11b) is peeled from the charging belt (13). The concentration of the polymer is higher in the 1 st solution (16) than in the 2 nd solution (17).)

1. A method for producing a nonwoven fabric, comprising inducing a charged solution containing a polymer and a solvent onto a collector charged to the opposite polarity to the solution or to a long length at which the potential is zero, and collecting fibers formed from the polymer as a nonwoven fabric, wherein:

the long collector electrode is moved in the longitudinal direction, and the method for producing a nonwoven fabric includes:

a 1 st layer forming step of forming a 1 st layer made of 1 st fibers on the moving collector by charging the 1 st solution with a 1 st rotating conductor formed of a conductor while rotating in contact with the 1 st solution disposed below the collector;

a 2 nd layer forming step of forming a 2 nd layer made of 2 nd fibers in a state of being overlapped with the 1 st layer by electrically charging the 2 nd solution with a 2 nd rotating conductor formed of a conductor while rotating in contact with a 2 nd solution disposed downstream of the 1 st solution in a moving direction of the collecting electrode and below the collecting electrode; and

a peeling step of peeling the nonwoven fabric provided with the 1 st layer and the 2 nd layer from the collector electrode,

the concentration of the polymer is higher in the 1 st solution than in the 2 nd solution.

2. The method for producing a nonwoven fabric according to claim 1,

said difference in concentration between said 1 st solution and said 2 nd solution is at least 1%.

3. The method for producing a nonwoven fabric according to claim 1 or 2,

the distance between the 1 st rotating conductor and the 2 nd rotating conductor and the collector is the same.

4. The nonwoven fabric production method according to any one of claims 1 to 3,

the 1 st and 2 nd rotary conductors have the same potential difference with the collector.

5. The nonwoven fabric production method according to any one of claims 1 to 4,

the distance from the rotation center to the periphery of the 1 st rotating conductor is constant.

6. The nonwoven fabric production method according to any one of claims 1 to 4,

the 1 st rotating conductor is provided with a plurality of protrusions on the periphery, and the distances from the vertexes of the protrusions to the rotation center are the same.

7. The nonwoven fabric production method according to any one of claims 1 to 6,

the polymer is at least one of cellulose triacetate, cellulose diacetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, nitrocellulose, ethyl cellulose and carboxymethyl ethyl cellulose.

8. The nonwoven fabric production method according to any one of claims 1 to 7,

the solvent contains at least one of dichloromethane, chloroform, methyl acetate and acetone.

9. A nonwoven fabric manufacturing apparatus that traps fibers formed of a polymer as a nonwoven fabric by inducing a charged solution containing the polymer and a solvent onto a collector that is charged to an opposite polarity to the solution or set to a potential zero, the nonwoven fabric manufacturing apparatus comprising:

a long dimension of the collector electrode;

a moving mechanism that moves the collector electrode in a longitudinal direction;

a 1 st container which contains the 1 st solution and is disposed below the collecting electrode;

a 1 st rotating conductor which rotates while being in contact with the 1 st solution and is formed of a conductor;

a 2 nd container which contains the 2 nd solution and is disposed downstream of the 1 st container and below the collecting electrode in the moving direction of the collecting electrode;

a 2 nd rotating conductor which rotates while being in contact with the 2 nd solution in the 2 nd container and is formed of a conductor; and

a potential difference generator that generates a potential difference between the 1 st and 2 nd rotary conductors and the collector,

the concentration of the polymer is higher in the 1 st solution than in the 2 nd solution.

Technical Field

The invention relates to a method and equipment for manufacturing non-woven fabric.

Background

For example, there is a nonwoven fabric formed of so-called fibers having a diameter of several nm or more and less than 1000 nm. As a method for producing a nonwoven fabric formed of such ultrafine fibers, a method using an electric field spinning method (also referred to as an electrospinning method or an electrodeposition method) is known. This method is performed, for example, using an electrospinning device having a nozzle, a collector electrode, and a voltage applying unit, and a voltage is applied between the nozzle and the collector electrode by the voltage applying unit. This charges the nozzle positively and charges the collector negatively, for example. In a state where a voltage is applied, a solution in which a raw material of a fiber (hereinafter, referred to as a fiber material) is dissolved in a solvent is discharged from an opening of a nozzle. The solution discharged from the nozzle forms fibers while being guided to the collector, and the fibers are collected on the collector as a nonwoven fabric.

When a nozzle is used, the fiber material dissolved in the solution may be solidified at the opening, and the opening may be closed. Therefore, there is a limit to the time for continuously forming the fibers. As a result, there is a limitation in continuously producing nonwoven fabrics.

When the nonwoven fabric formed on the collecting electrode is used, the nonwoven fabric is peeled off from the collecting electrode. However, when the nonwoven fabric is peeled off, the nonwoven fabric and the collector electrode are bonded to each other with too strong adhesion, and thus a part of the nonwoven fabric may remain on the collector electrode or the nonwoven fabric may be broken. Regarding such peelability, for example, patent document 1 describes the following technique: in the electrospinning method, the adhesion between the nonwoven fabric and the collecting electrode can be adjusted by adjusting the distance between the portion from which the solution is discharged and the collecting electrode. In patent document 1, a rotating member composed of a rotating shaft and a disk is brought into contact with a solution in which a fiber material is dissolved, and the rotating member is rotated to form a state in which the solution is applied to the entire side surface of the disk. Further, a method of flying a solution from a rotating member is also described in patent document 2.

Prior art documents

Patent document

Patent document 1: japanese patent laid-open No. 2014-227629

Patent document 2: japanese Kokai publication No. 2007-505224

Disclosure of Invention

Technical problem to be solved by the invention

The methods of patent documents 1 and 2 have an advantage in that the fibers can be continued for a long time because they do not use a nozzle. However, in the methods of patent documents 1 and 2, as described in patent document 1, in order to improve the peeling property from the collecting electrode, it is not easy to find conditions for obtaining a target nonwoven fabric when the distance between the rotating member and the collecting electrode is adjusted. This is because the distance between the rotating member and the collecting electrode greatly affects the diameter of the fibers, the adhesion between the fibers in the nonwoven fabric, and the like. As described above, the methods of patent documents 1 and 2 are not easy to find conditions for obtaining a nonwoven fabric aimed at improving the peelability.

Accordingly, an object of the present invention is to provide a method and an apparatus for producing a nonwoven fabric, which can improve the peelability from a collecting electrode and can continuously produce a nonwoven fabric for a longer period of time.

Means for solving the technical problem

The method for producing a nonwoven fabric of the present invention comprises a 1 st layer forming step, a 2 nd layer forming step, and a peeling step, wherein a long collecting electrode is moved in the longitudinal direction, a charged solution containing a polymer and a solvent is induced to the collecting electrode charged to the opposite polarity to that of the solution or set to zero potential, and fibers formed of the polymer are collected as a nonwoven fabric. In the 1 st layer forming step, the 1 st solution is rotated while being in contact with the 1 st solution disposed below the collector, and the 1 st rotating conductor formed of a conductor charges the 1 st solution, thereby forming the 1 st layer composed of the 1 st fibers on the moving collector. In the 2 nd layer forming step, the 2 nd rotating conductor which is formed of a conductor and rotates while being in contact with the 2 nd solution disposed downstream of the 1 st solution in the moving direction of the collecting electrode and below the collecting electrode charges the 2 nd solution, thereby forming the 2 nd layer composed of the 2 nd fibers in a state of being overlapped with the 1 st layer. In the peeling step, the nonwoven fabric having the 1 st and 2 nd layers is peeled from the collector. The concentration of polymer is higher in the 1 st solution than in the 2 nd solution.

Preferably, the difference in concentration between the 1 st solution and the 2 nd solution is at least 1%.

Preferably, the distance from the 1 st rotating conductor to the collector is the same as that from the 2 nd rotating conductor.

Preferably, the potential difference between the 1 st rotating conductor and the 2 nd rotating conductor and the collector is the same.

Preferably, the distance from the center of rotation to the periphery of the 1 st rotating conductor is constant.

Preferably, the 1 st rotating conductor has a plurality of projections on a peripheral edge thereof, and the apexes of the plurality of projections are spaced from the rotation center by the same distance.

Preferably, the polymer is at least one of cellulose triacetate, cellulose diacetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, nitrocellulose, ethyl cellulose, and carboxymethylethylcellulose.

Preferably, the solvent contains at least one of dichloromethane, chloroform, methyl acetate, and acetone.

A nonwoven fabric manufacturing apparatus of the present invention comprises a long collecting electrode, a moving mechanism, a 1 st container, a 1 st rotating conductor, a 2 nd container, a 2 nd rotating conductor, and a potential difference generator, and collects fibers made of a polymer as a nonwoven fabric by charging a charged solution containing the polymer and a solvent to the collecting electrode having a polarity opposite to that of the solution or having a potential of zero. The moving mechanism moves the collector electrode in the longitudinal direction. The 1 st container contains the 1 st solution and is disposed below the collecting electrode. The 1 st rotating conductor is formed of a conductor and rotates while contacting the 1 st solution. The 2 nd container contains the 2 nd solution and is disposed downstream of the 1 st container and below the collecting electrode in the moving direction of the collecting electrode. The 2 nd rotating conductor rotates while contacting the 2 nd solution in the 2 nd container, and is formed of a conductor. The potential difference generator generates a potential difference between the 1 st and 2 nd rotary conductors and the collector. The concentration of the polymer in the 1 st solution is higher than that in the 2 nd solution.

Effects of the invention

According to the present invention, the non-woven fabric can be continuously produced for a longer period of time while improving the peelability from the collecting electrode.

Drawings

FIG. 1 is a schematic view of a nonwoven fabric manufacturing apparatus.

Fig. 2 is an explanatory view of the 1 st rotary conductor.

Fig. 3 is a schematic view of a nonwoven fabric manufacturing apparatus.

Fig. 4 is an explanatory diagram of the 1 st rotary conductor and the 2 nd rotary conductor.

Fig. 5 is a schematic view of a rotating plate.

Detailed Description

Fig. 1 is a schematic view of a nonwoven fabric production apparatus 10 according to an embodiment of the present invention, which is used for continuously producing a nonwoven fabric 11. The nonwoven fabric 11 can be used as, for example, a wiping cloth, a filter cloth, a medical nonwoven fabric (referred to as a drape) with which a wound or the like is in contact, or the like.

The nonwoven fabric 11 is formed of 2 kinds of nanofibers 12 different in diameter from each other, and has a 2-layer structure in which a 1 st layer 11a and a 2 nd layer 11b overlap in the thickness direction. The 1 st layer 11a is composed of 1 st fibers 12a having a relatively large diameter. The 2 nd layer 11b is composed of the 2 nd fibers 12b having a smaller diameter. In addition, when the 1 st fiber 12a and the 2 nd fiber 12b are not distinguished, these are collectively referred to as nanofibers 12.

The 1 st layer 11a is formed directly on the surface of the charging belt 13 described later, and the 2 nd layer 11b is formed on the surface of the 1 st layer 11a opposite to the charging belt 13 side. In this example, the layer overlapping with the 1 st layer 11a is only the 1 st layer 11b, that is, the 2 nd layer 11b, and another layer may be further formed on the surface of the 2 nd layer 11 b. The nonwoven fabric is not limited to such a 2-layer structure, and may be formed of, for example, 3 or more types of nanofibers 12 having different diameters. The charging belt 13 is an example of a collector that collects the nanofibers 12 as the nonwoven fabric 11. The charging belt 13 is formed in a long length, in this example, an endless belt, and moves in the longitudinal direction. The nonwoven fabric 11 thus produced is peeled from the charging belt 13 and used for the various applications as described above.

The 1 st fiber 12a has a diameter Da in a range of more than 1 × Db and 3 × Db or less, assuming that the diameter of the 2 nd fiber 12b is Db. The diameter Db of the 2 nd fiber 12 is preferably in the range of 50nm or more and 3000nm or less.

The nanofibers 12 are formed from a solution in which a polymer as a nanofiber material is dissolved in a solvent by an electrospinning method. The solution for forming the 1 st fibers 12a is referred to as a 1 st solution 16, and the solution for forming the 2 nd fibers 12b is referred to as a 2 nd solution 17. The nonwoven fabric manufacturing apparatus 10 includes a 1 st container 21 for containing the 1 st solution 16 and a 2 nd container 22 for containing the 2 nd solution 17. The 1 st container 21 and the 2 nd container 22 are disposed below the charging belt 13. The 2 nd container 22 is disposed downstream of the 1 st container 21 in the moving direction of the charging belt 13. Therefore, the 2 nd solution 17 is located downstream of the 1 st solution 16 in the moving direction of the charging belt 13.

The polymers contained in the 1 st solution 16 and the 2 nd solution 17 are preferably thermoplastic resins, and among them, cellulose-based polymers are preferable. The cellulose-based polymer is preferably at least one of cellulose triacetate (hereinafter, TAC), cellulose diacetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, nitrocellulose, ethylcellulose, and carboxymethylethylcellulose. When these polymers are used, a solvent that evaporates relatively easily can be used, and thus the degree of freedom in the diameter of the nanofibers 12 that can be formed is large. That is, the nanofibers 12 having a small diameter (thin) can be formed similarly to other polymers, and the nanofibers 12 having a large diameter (thick) can be easily formed. Therefore, the nonwoven fabric 11 can be easily manufactured according to the application. Further, when these polymers are used, the improvement of the releasability from the charging belt 13, which will be described later, is more remarkable.

The 1 st solution 16 and the 2 nd solution 17 may contain the same polymer or different polymers. In this example, the same polymer is used for the 1 st solution 16 and the 2 nd solution 17.

The solvent contained in the 1 st solution 16 and the 2 nd solution 17 is not particularly limited as long as it is a compound capable of dissolving the liquid of the polymer as the fiber material. When the polymer is the cellulose-based polymer, it is preferable to use a solvent that is easily evaporated even at a relatively low temperature, from the viewpoint of easily adjusting the diameter of the nanofibers 12 to be fine or coarse. Examples of such a solvent include at least one of dichloromethane (hereinafter referred to as DCM), chloroform, methyl acetate, and acetone. Also, the solvent may be a mixture of a plurality of compounds. As the mixture, a mixture of methanol (hereinafter referred to as MeOH), ethanol, and N, N-dimethylformamide mixed with at least one of DCM, chloroform, methyl acetate, and acetone is preferable. As described later, the solvent is preferably a mixture from the viewpoint of easily adjusting the evaporation rates of the 1 st solution 16 and the 2 nd solution 17 in flight.

The solvents of the 1 st solution 16 and the 2 nd solution 17 may be the same as or different from each other. The solvents of the 1 st solution 16 and the 2 nd solution 17 preferably contain a common component. In this example, the solvents of the 1 st solution 16 and the 2 nd solution 17 were mixed to have the same formulation (components and mixing ratio of each component).

The concentration of polymer is higher in the 1 st solution 16 than in the 2 nd solution 17. The concentration difference between the polymers of the 1 st solution 16 and the 2 nd solution 17 is preferably at least 1%, that is, preferably 1% or more. The concentration difference of the polymer is more preferably in the range of 1% to 10%, and still more preferably in the range of 1% to 5%.

The nonwoven fabric manufacturing apparatus 10 includes a 1 st rotating conductor 23 and a 2 nd rotating conductor 24 formed of a conductor. The 1 st rotating conductor 23 and the 2 nd rotating conductor 24 are used to electrically charge the 1 st solution 16 and the 2 nd solution 17 and fly the solutions in filament shapes. The 1 st rotating conductor 23 and the 2 nd rotating conductor 24 have a rotating mechanism 27. The 1 st rotating conductor 23 is provided in the 1 st vessel 21 having an open upper portion. The 1 st rotating conductor 23 includes a rotating shaft 23a rotated by the rotating mechanism 27 and a circular disk 23b fixed to the rotating shaft 23 a. A circular opening 23o is formed in the center of the disc 23b, and the opening 23o and the rotary shaft 23a are fixed in a fitted state. Thereby, the disc 23b rotates integrally with the rotary shaft 23a in the circumferential direction. The disc 23b is disposed in a state in which at least a part of the peripheral edge thereof protrudes from the liquid surface of the 1 st solution 16. Thereby, the 1 st rotating conductor 23 rotates while contacting the 1 st solution 16. By the rotation, at least the periphery of the disk 23b protruding from the liquid surface of the 1 st solution 16 is in a state where the 1 st solution 16 is attached.

Both the rotary shaft 23a and the disc 23b are formed of a conductor, and the rotary shaft 23a is connected to the voltage applying section 28. When a voltage is applied by the voltage applying unit 28, the 1 st solution 16 is charged to the 1 st polarity.

Although the number of the 1 st rotating conductors 23 in this example is 1, a plurality of them may be arranged in the moving direction of the charging belt 13. When a plurality of 1 st rotating conductors 23 are provided, a plurality of 1 st rotating conductors 23 may be arranged in one 1 st container 21, or a plurality of 1 st containers 21 may be arranged in the moving direction of the charging belt 13, and the 1 st rotating conductors 23 may be provided in the respective 1 st containers 21.

The 2 nd rotating conductor 24 is provided in the 2 nd container 22 having an open upper portion. The 2 nd rotating conductor 24 is configured similarly to the 1 st rotating conductor 23, that is, includes a rotating shaft 24a rotated by the rotating mechanism 27 and a circular disk 24b fixed to the rotating shaft 24 a. A circular opening 24o is formed in the center of the disc 24b, and the opening 24o and the rotary shaft 24a are fixed in a fitted state. Thereby, the disc 24b rotates integrally with the rotary shaft 24a in the circumferential direction. The disc 24b is disposed in a state in which at least a part of the peripheral edge thereof protrudes from the liquid surface of the 2 nd solution 17. Thereby, the 2 nd rotating conductor 24 rotates while contacting the 2 nd solution 17. By the rotation, the 2 nd solution 17 is attached to the periphery of the disk 24b protruding from the liquid surface of the 2 nd solution 17.

Both the rotary shaft 24a and the disc 24b are formed of a conductor, and the rotary shaft 24a is connected to the voltage application part 28. The rotation shaft 24a and the rotation shaft 23a are connected in parallel to the voltage applying unit 28. When a voltage is applied by the voltage applying unit 28, the 2 nd solution 17 attached to the peripheral edge of the disk 24b protruding from the liquid surface is also charged to the 1 st polarity which is the same polarity as the 1 st solution 16.

As the above-mentioned conductors as the raw materials of the 1 st rotating conductor 23 and the 2 nd rotating conductor 24, some metal material having corrosion resistance to the solvent used for the 1 st solution 16 and the 2 nd solution 17 and having conductivity is used. In the examples described later, since DCM is used for the solvent components of the 1 st solution 16 and the 2 nd solution 17, stainless steel is used as the conductor from the viewpoint of both corrosion resistance to DCM and conductivity. The conductor is not limited to stainless steel, and for example, hastelloy (registered trademark) of Haynes International, inc, titanium alloy, steel, or copper can be preferably used. Further, the hastelloy alloy (registered trademark) is a nickel-based alloy (an alloy obtained by adding molybdenum and/or chromium to nickel).

In this example, 32 nd rotating conductors 24 are provided in 12 nd container 22, and they are arranged side by side in the moving direction of the charging belt 13. However, the 2 nd container 22 may be provided in a state where 3 containers are arranged in the moving direction of the charging belt 13, and the 2 nd rotating conductor 24 may be provided in each 2 nd container 22. In this manner, the number of the 2 nd rotating conductors 24 provided in the 1 nd 2 nd container 22 is not particularly limited. The number of the 2 nd rotating conductors 24 is not limited to 3 in this example, and may be 1, 2, or 4 or more.

When the voltage applying unit 28 is connected to the rotating shafts 23a and 24a, the rotating shafts 23a and 24a may be electrically connected to the disc 24 b. Therefore, the entirety of each of the rotary shafts 23a, 24a and the disc 24b does not need to be formed of a conductor.

The nonwoven fabric production apparatus 10 further includes a collection unit 32 and the voltage application unit 28. The collection unit 32 includes the charging belt 13, a moving mechanism 33, a winding unit 34, and a roller 35. The charging belt 13 is formed in a ring shape as a metal belt. The charging belt 13 is made of a material charged by applying a voltage by the voltage applying unit 28, and is made of, for example, stainless steel.

The moving mechanism 33 is constituted by a pair of rollers 37 and 38, a motor 41, and the like. The charging belt 13 is horizontally wound around a pair of rollers 37, 38. A motor 41 disposed outside the spinning chamber 42 is connected to each shaft of one of the rollers 37 and 38, and the rollers 37 and 38 are rotated at a predetermined speed. The charging belt 13 moves in the longitudinal direction by this rotation, and circulates between the roller 37 and the roller 38. In the present embodiment, the moving speed of the charging belt 13 is set to 10 cm/hour, but the present invention is not limited thereto. In addition, only one of the pair of rollers 37, 38 may be rotated by the motor 41.

The voltage applying unit 28 is an example of a potential difference generator that generates a potential difference between the 1 st rotating conductor 23 and the 2 nd rotating conductor 24 and the charging belt 13. The voltage applying unit 28 is connected to the 1 st rotating conductor 23, the 2 nd rotating conductor 24, and the charging belt 13, and applies a voltage thereto. Thereby, the 1 st rotating conductor 23 and the 2 nd rotating conductor 24 are charged to the 1 st polarity, and the charging belt 13 is charged to the 2 nd polarity, which is the opposite polarity to the 1 st polarity. The 1 st solution 16 is charged to the 1 st polarity by being brought into contact with the disk 23b of the 1 st rotating conductor 23 which has been charged. Then, the 1 st solution 16 adhering to the rotating disk 23b is induced to the charging belt 13 charged to the 2 nd polarity at a position above the liquid surface of the 1 st solution 16, and flies toward the charging belt 13 in a filamentous shape. Similarly to the 2 nd solution 17, the charged first solution is charged to the 1 st polarity which is the same as the 1 st solution 16 by contacting the disk 24b of the 2 nd rotating conductor 24, and flies in a thread-like shape from the disk 24b on the liquid surface of the 2 nd solution 17 toward the charging belt 13 in the charged state.

Since the 1 st solution 16 and the 2 nd solution 17 are flown from the 1 st rotating conductor 23 and the 2 nd rotating conductor 24, the nanofibers 12 can be stably formed for a long time. For example, the nozzle is not blocked by polymer curing as in the nozzle approach. The 1 st rotating conductor 23 and the 2 nd rotating conductor 24 are repeatedly immersed in the 1 st solution 16 and the 2 nd solution 17 contained in the 1 st container 21 and the 2 nd container 22, whereby the solidification of the polymer is suppressed and the polymer is dissolved even in the case of a slight solidification. Since the nanofibers 12 can be stably formed for a long period of time, the nonwoven fabric 11 can be formed in a longer size, or the nonwoven fabric 11 having a greater thickness can be manufactured.

In the moving charging belt 13, the 1 st fiber 12a formed of the 1 st solution 16 located on the upstream side of the 2 nd solution 17 in the moving direction of the charging belt 13 is first collected and deposited to form the 1 st layer 11a (1 st layer forming step). Next, the 2 nd fibers 12b formed from the 2 nd solution 17 are collected and accumulated in the 1 st layer 11a, and the 2 nd layer 11b is formed to overlap the 1 st layer 11a (2 nd layer forming step). In this way, the 1 st fibers 12a and the 2 nd fibers 12b are collected as the nonwoven fabric 11. In fig. 1, one of the pair of rollers 37 and 38 on the left side of the sheet is a roller 37, and the other on the right side is a roller 38, and the nonwoven fabric 11 is formed on the charging belt 13 from the roller 37 toward the roller 38.

The 2 nd layer 11b is a layer that plays a target function as the nonwoven fabric 11. Therefore, the 2 nd fibers 12b constituting the 2 nd layer 11b are set to a diameter corresponding to the target function. For example, if the nonwoven fabric 11 having a higher porosity is used according to the target function, the 2 nd fibers 12b constituting the 2 nd layer 11b are formed to be finer. However, the finer the nanofibers 12 in contact with the charging belt 13, the stronger the adhesion between the nonwoven fabric and the charging belt, and therefore, when the nonwoven fabric is peeled as described later, the nonwoven fabric is broken or peeling residue is likely to be generated in the charging belt 13.

In this regard, in this example, the 1 st solution 16 has a higher concentration of polymer than the 2 nd solution 17, and therefore, the 1 st fibers 12a are formed to be thicker than the 2 nd fibers 12 b. As a result, the 1 st layer 11a is formed in the 1 st fibers 12a in a state of being in contact with the charging belt 13, and therefore the nonwoven fabric 11 having a reduced adhesion with the charging belt 13 can be obtained. Therefore, when the nonwoven fabric 11 is peeled, the nonwoven fabric 11 can be peeled with a weaker force, and the breakage of the nonwoven fabric 11 and the peeling on the charging belt 13 are also suppressed. By spinning the 1 st solution 16 having a higher polymer concentration than the 2 nd solution 17 before the 2 nd solution 17 in this manner, the peelability is improved as described above. According to this method, for example, even if the distance L1 described later is not adjusted, the peelability can be improved only by preparing the 1 st solution 16 in advance to a higher concentration than the 2 nd solution 17.

When the 1 st layer 11a is formed only for the purpose of improving the peelability, the 2 nd layer 11b is a so-called nonwoven fabric main body that serves the intended function as the nonwoven fabric 11 as described above, and therefore the 2 nd layer 11b occupies most of the thickness of the nonwoven fabric 11. From the viewpoint of improving the peelability, the 1 st layer 11a is reliable if it is formed to have a thickness of at least 0.02mm, that is, a thickness of 0.02mm or more, and is set to be in a range of 0.02mm or more and 0.2mm or less in the embodiment described later.

The layer 1a can also serve the intended function of the nonwoven fabric 11 in addition to improving the peelability. In this case, the thickness of the 1 st layer 11a may be the same as or greater than the 2 nd layer 11b or the 2 nd layer 11 b.

The difference in polymer concentration between the 1 st solution 16 and the 2 nd solution 17 is at least 1%, and therefore the improvement in the releasability is more reliable. The solvents of the 1 st solution 16 and the 2 nd solution 17 contain a common component, and therefore, even if the conditions for forming the 1 st fibers 12a and the 2 nd fibers 12b are made the same, the 1 st fibers 12a and the 2 nd fibers 12b are easily formed to have different diameters from each other. In this example, a mixture having the same formulation, i.e., the same components and the same blending ratio of the components is used as the solvent for the 1 st solution 16 and the 2 nd solution 17, and therefore the effect is more remarkable.

The 1 st rotating conductor 23 and the 2 nd rotating conductor 24 are connected in parallel to the voltage applying unit 28, respectively. Thereby, the potentials of the disk 23b and the disk 24b become equal, and therefore the potentials of the 1 st solution 16 and the 2 nd solution 17 become equal, and therefore the potential differences with the charging belt 13 become equal to each other. As a result, the difference in the concentration of the polymers of the 1 st solution 16 and the 2 nd solution 17 more reliably serves as the difference in the diameter of the fiber 12.

The roller 35 is provided between the charging belt 13 and the winding unit 34, and supports the nonwoven fabric 11 toward the winding unit 34. Thereby, the nonwoven fabric 11 is stably peeled from the charging belt 13 at a predetermined position (peeling step). The spinning chamber 42 accommodates, for example, the 1 st vessel 21, the 2 nd vessel 22, and a part of the collecting section 32. The spinning chamber 42 is configured to be hermetically sealable, thereby preventing leakage of solvent gas or the like to the outside. The solvent gas is a gas in which the solvents of the 1 st solution 16 and the 2 nd solution 17 are vaporized.

The winding section 34 has a winding shaft 45. The winding shaft 45 is rotated by a motor (not shown), and the nonwoven fabric 11 is wound around a winding core 46 provided on the winding shaft 45. The long nonwoven fabric 11 obtained by continuous production is cut into a size and a shape corresponding to the application and used.

The voltage applied by the voltage applying unit 28 is preferably in the range of 5kV or more and 100kV or less. By being 5kV or more, the 1 st solution 16 and the 2 nd solution 17 are more easily induced to the charging belt 13 than in the case of being less than 5 kV. By setting the voltage to 100kV or less, the formation of droplets of the 1 st solution 16 and the 2 nd solution 17 is more reliably suppressed in the spinning space between the 1 st rotating conductor 23 and the 2 nd rotating conductor 24 and the charging belt 13 than in the case of more than 100 kV. Therefore, the beads (micro beads) can be prevented from being mixed into the nonwoven fabric.

The voltage applied by the voltage application unit 28 is more preferably in the range of 10kV or more and 80kV or less, still more preferably in the range of 20kV or more and 60kV or less, and particularly preferably in the range of 30kV or more and 50kV or less.

In the present embodiment, the 1 st rotating conductor 23 and the 2 nd rotating conductor 24 are positively charged (+) and the potential is set to zero by grounding the charging belt 13, but the charging belt 13 may be charged negatively (-) with a polarity opposite to that of the 1 st rotating conductor 23 and the 2 nd rotating conductor 24. Further, the 1 st rotating conductor 23 and the 2 nd rotating conductor 24 may be negatively charged, and the charging belt 13 may be negatively charged. Further, an ion wind supply device that blows an ion wind on the surface of the charging belt 13 facing the roller 38 from the roller 37 on the side opposite to the surface on which the nonwoven fabric 11 is formed may be provided as the potential difference generator. The ion wind supply device may be used instead of the voltage application unit 28, or may be used together with the voltage application unit 28. This enables charging the charging belt 13 to the 2 nd polarity or potential adjustment.

The distances L1 (see fig. 2) between the 1 st rotating conductor 23 and the 2 nd rotating conductor 24 and the charging belt 13 are preferably equal to each other, and are the same in this example. The distance L1 is the distance between the disks 23b, 24b and the charging belt 13 in this example. In fig. 2, the distance L1 is shown only by the 1 st rotating conductor 23, and the same applies to the 2 nd rotating conductor 24. Since the distances L1 between the 1 st rotating conductor 23 and the 2 nd rotating conductor 24 are equal to each other, the potential difference with the charging belt 13 is also equal to each other. As a result, the difference in the concentration of the polymers of the 1 st solution 16 and the 2 nd solution 17 more reliably serves as the difference in the diameter of the fiber 12.

The appropriate value of the distance L1 varies depending on the types of the polymer and the solvent 26 as the fiber material, the concentrations of the polymer in the 1 st solution 16 and the 2 nd solution 17, and the like, and is preferably in the range of 50mm to 300mm, and is 150mm in the present embodiment.

As shown in fig. 2, the 1 st rotating conductor 23 may be disposed in a state where a part of the disk 23b, which is a flight source of the 1 st solution 16, is discharged from the liquid surface of the 1 st solution 16 stored in the 1 st container 21. Thus, the 1 st solution 16 is continuously applied to the rotating disk 23b, and the potential difference with the charging belt 13 is reliably maintained, so that the continuous flight is more reliable. The same applies to the 2 nd rotary conductor 24.

Here, the diameter of the disc 23b is D1, the distance from the liquid surface of the 1 st solution 16 to the uppermost position of the disc 23b is D2, and the distance from the liquid surface to the lowermost position of the disc 23b is D3. The ratio D3/D1 obtained by dividing the distance D3 by the diameter D1 is preferably in the range of 0.001 or more and less than 1. By setting the D3/D1 to 0.001 or more, the 1 st solution 16 sufficient to form the 1 st fibers 12a is supplied to the disc 23b as compared with the case of less than 0.001. When the ratio D3/D1 is less than 1, the amount of nanofibers 12 formed per unit time is larger than that in the case of 1 or more, and the state of the potential difference with the charging belt 13 is reliably maintained.

The ratio D3/D1 is more preferably in the range of 0.01 to 0.8, still more preferably in the range of 0.1 to 0.7, and particularly preferably in the range of 0.3 to 0.6. The same applies to the 2 nd rotary conductor 24.

Since the disk 23b is a perfect circle as described above, the distance D4 from the center CR of rotation to the peripheral edge is constant. Accordingly, the distance of the rotating disk 23b from the charging belt 13 is maintained constant, and thus the 1 st fiber 12a is stably and continuously formed. The same applies to the disc 24 b.

The 1 st rotating conductor 23 and the 2 nd rotating conductor 24 are configured similarly to the 1 st rotating conductor 23. Therefore, in fig. 3, the 1 st rotating conductor 23 is illustrated, and the 1 st rotating conductor 23 is explained with reference to fig. 3, and the explanation is omitted with respect to the 2 nd rotating conductor 24. As shown in fig. 3, the 1 st rotating conductor 23 is more preferably configured to have a plurality of disks 23b on the rotating shaft 23a, from the viewpoint of more significantly producing the nonwoven fabric 11. The 1 st rotating conductor 23 is disposed in a state where the longitudinal direction of the rotating shaft 23a coincides with the width direction of the charging belt 13. However, the 1 st rotating conductor 23 may be disposed in a state where the longitudinal direction of the rotating shaft 23a intersects (but is not orthogonal to) the width direction of the charging belt 13.

In fig. 3, for convenience, the number of the disks 23b provided on the rotating shaft 23a is drawn to 5, and the number of the disks 23b is 15 in this example, and is not particularly limited. The pitch P1 between the disks 23b is preferably determined according to a set value of the potential difference between the charging belt 13 and the 1 st rotating conductor 23, and is preferably in a range of 2mm to 50mm, for example. The thickness of the disks 23b is set to a thickness at which the disks 23b do not contact each other, and may be, for example, 1mm or less, in this example, 1 mm. By setting the pitch P1 to 2mm or more, the 1 st fibers 12a fly more reliably from the respective disks 23 b. By setting the pitch P1 to 50mm or less, the thickness unevenness of the 1 st layer 11a is more reliably suppressed. The pitch P1 is a distance between centers of the adjacent disks 23b in the thickness direction.

As shown in fig. 4, the rotation shaft 23a and the plurality of rotation shafts 24a are preferably provided in parallel with each other, in this example as well. In addition, if the angle formed by the two is within 5 °, the two are regarded as parallel. In this example, although the 1 st rotating conductor 23 and the plurality of 2 nd rotating conductors 24 are arranged so that the disks 23b and the disks 24b are aligned in a straight line in the moving direction of the charging belt 13, the disks 23b and the disks 24b of the respective 2 nd rotating conductors 24 do not necessarily have to be aligned in a straight line in the moving direction of the charging belt 13.

The pitches P2 of the rotating shafts 23a and 24a adjacent to each other in the moving direction of the charging belt 13 may be the same as each other or different from each other. The pitch P2 between the plurality of rotating shafts 24a provided in one 2 nd container 22 is set in a state where the disks 24b do not abut against each other. The pitch P2 is the distance between the centers of the rotating shafts 23a and 24a adjacent to each other in the moving direction of the charging belt 13.

The distance D5 between the rotating shafts 23a, 24a adjacent to each other in the moving direction of the charging belt 13 is preferably determined according to a set value of the potential difference between the charging belt 13 and the 1 st and 2 nd rotating conductors 23, 24, and is preferably in a range of 10mm to 200mm, for example. When the distance D5 is 10mm or more, the 1 st fibers 12a fly out of the respective disks 23b more reliably, and the 2 nd fibers 12b fly out of the respective disks 24b more reliably. When the distance D5 is 200mm or less, the amount of nanofibers 12 formed per unit time is larger, and the productivity of the nonwoven fabric 11 is good.

The 1 st rotating conductor 23 and the 2 nd rotating conductor 24 are not limited to the above examples. For example, a rotating plate 61 shown in fig. 5 may be used instead of the disks 23b, 24 b. The rotating plate 61 includes a plurality of projections 61a on the periphery. The rotating plate 61 of fig. 5 includes 10 protrusions 61a, but the number of the protrusions 61a is not limited to 10, and may be at least 2. The projection 61a has an inverted V-shape as shown in fig. 5. The rotating plate 61 is configured as a 1 st rotating conductor and a 2 nd rotating conductor in a state where the rotating shaft 23a and the rotating shaft 24a are inserted into the opening 61b at the center and fixed to the rotating shafts 23a and 24 a.

When the 1 st and 2 nd rotary conductors provided with the rotary plate 61 are used, the apexes 61t of the projections 61a serve as flight sources of the 1 st and 2 nd solutions 16 and 17, and the projections fly from the apexes 61 t. This is considered to be because the electric field is concentrated on the vertex 61 t. Therefore, compared with the case of using the disks 23b and 24b, the applied voltage can be suppressed to be low, and the energy saving effect is obtained. For example, it was confirmed that the nanofibers 12 can be formed at about 20kV when the rotary plate 61 is used, as compared with the case where the applied voltage is about 40kV when the disks 23b and 24b are used. Moreover, the rotating plate 61 has the following advantages: since the range in which the applied voltage can be set is wider than the disks 23b and 24b, the degree of freedom in the diameter of the nanofiber 12 that can be formed is greater than that of the disks 23b and 24 b.

The distances D6 from the center of rotation CR to the apex 61t when the rotating plate 61 is fixed to the rotating shafts 23a, 24a of the plurality of projections 61a are the same as each other. As a result, the potential difference between the apex 61t and the charging belt 13 during rotation becomes equal, and as a result, the difference in the polymer concentration between the 1 st solution 16 and the 2 nd solution 17 is more reliably displayed as a difference in the diameter of the fiber 12. The distances D6 are considered to be the same as each other as long as they are within 1 mm. In the rotating plate 61, as shown in fig. 5, the largest diameter is defined as the diameter D1.

Examples

[ example 1] to [ example 5]

A long nonwoven fabric 11 was produced by using a nonwoven fabric production apparatus 10, and examples 1 to 5 were set forth. However, instead of the 1 st rotary conductor 23 and the 2 nd rotary conductor 24, the 1 st rotary conductor and the 2 nd rotary conductor in which the rotary plate 61 is provided on the rotary shaft 23a and the rotary shaft 24a, respectively, are used.

The polymers of the 1 st solution 16 and the 2 nd solution 17 are TAC. In the column of "blending ratio" in table 1, the blending ratio of the 1 st component to the 2 nd component of the solvent is shown by the symbol of 1 st component: 2 nd component. The column of "concentration" in table 1 is a value (in%) obtained by { M1/(M1+ M2) } × 100, where the mass of the polymer is M1 and the mass of the solvent is M2. The column "concentration difference" is a value (in%) obtained by subtracting the concentration (in%) of the 2 nd solution from the concentration (in%) of the 1 st solution.

In either embodiment, the applied voltage is 40kV, the distance L1 is 150mm, and the moving speed of the charging belt 13 is 0.1 m/min.

In each example, the peelability of the nonwoven fabric 11 was evaluated by the following evaluation method and criteria. The evaluation results are shown in table 1.

The nonwoven fabric 11 was peeled from the charging belt 13, and the presence, absence and degree of the peeling residue on the charging belt were evaluated. First, an operation of grasping one end portion of the nonwoven fabric 11 on the charging belt 13 and pulling it up from the charging belt 13 is performed, and a partial region in the longitudinal direction of the nonwoven fabric 11 is peeled off as a sample. The peeled sample was weighed and the weight thereof was W1. The sample area of the charging belt 13 was peeled off by rubbing, and the nonwoven fabric sheet and fibers remaining in this area were collected as a peeling residue. The peeling residue portion was weighed and its weight was set to W2. Then, using the value (unit%) obtained by W2/(W1+ W2) × 100, evaluation was performed according to the following criteria. A to C are qualified, and D is unqualified. When the nonwoven fabric was broken during the peeling, the evaluation was D regardless of the presence or absence and the degree of the peeling residue.

A; 0% of stripping residue

B; the content of the peeling residue is more than 0% and less than 25%.

C; the content of the peeling residue is 25% or more and less than 50%.

D; the content of the peeling residue is 50% or more.

[ Table 1]

Comparative example 1

The nonwoven fabric was produced by using only the 2 nd solution 17 without using the 1 st solution 16 and the 1 st rotating conductor 23. The applied voltage, the distance L1, and the moving speed of the charging belt 13 are the same as those of the embodiment.

The releasability was evaluated in the same manner and in the same manner as in examples. The evaluation results are shown in Table 1.

Description of the symbols

10-nonwoven fabric manufacturing equipment, 11-nonwoven fabric, 11 a-1 st layer, 11 b-2 nd layer, 12-nanofiber, 12 a-1 st fiber, 12 b-2 nd fiber, 13-charging belt, 16, 17-1 st solution, 2 nd solution, 21, 22-1 st container, 2 nd container, 23, 24-1 st rotating conductor, 2 nd rotating conductor, 23a, 24 a-rotating shaft, 23b, 24 b-disk, 27-rotating mechanism, 28-voltage applying part, 32-collecting part, 33-moving mechanism, 34-winding part, 35-roller, 37, 38-roller, 41-motor, 42-spinning chamber, 45-winding shaft, 46-winding core, 61-rotating plate, 61 a-bulge, 23 o-winding shaft, 35-roller, 37, 38-roller, 41-motor, 42-spinning chamber, 45-winding shaft, 61-winding core, 61-rotating plate, 61 a-bulge, 23 a-winding shaft, 24o, 61 b-opening, 61 t-apex, CR-center of rotation, L1, D2, D3, D4, D5, D6-distance, D1-diameter, P1, P2-spacing.