JP7511226B2 - Nonwoven fabric manufacturing method and nonwoven fabric manufacturing device - Google Patents

Description

The present invention relates to a method for manufacturing a nonwoven fabric, an apparatus for manufacturing a nonwoven fabric, and a nonwoven fabric.

Electrostatic spinning is commonly used as a method for producing nonwoven fabrics. Specific examples of electrostatic spinning include a method using a gas phase as the spinning site and a method using a liquid phase as the spinning site.

In electrostatic spinning, which uses the gas phase as the spinning site, a high voltage is applied to a solution containing a polymeric material, which causes the solution to be sprayed into the gas phase toward a collector (e.g., a metal plate or metal drum). The solvent evaporates from the solution moving through the gas phase, and a nonwoven fabric is formed from the polymeric material, and the nonwoven fabric is accumulated on the collector (see Non-Patent Document 1).

In electrostatic spinning, which uses a liquid phase as the spinning site, a high voltage is applied to a solution containing a polymeric material, which causes the solution to be sprayed into the liquid phase toward a counter electrode. The solvent is removed from the solution moving through the liquid phase, and a nonwoven fabric is formed from the polymeric material, and the nonwoven fabric is accumulated on the counter electrode, or floats throughout the liquid phase (see Patent Document 1).

Patent No. 5845525

Seeram Ramakrishna et al., An Introduction to Electrospinning and Nanofibers, World Scientific, 2005 https://doi.org/10.1142/5894

However, conventional electrospinning methods have the problem that the nonwoven fabric is not easy to recover because it accumulates on a collector or electrode, or floats throughout the liquid phase.

Specifically, when the nonwoven fabric is accumulated on a collector or electrode, it is necessary to peel the nonwoven fabric from the collector or electrode. In this case, there is a problem that this operation takes time. When the nonwoven fabric floats throughout the liquid phase, the nonwoven fabric is not accumulated in a designated place, and there is a problem that it takes time to collect the nonwoven fabric that is not accumulated.

One aspect of the present invention aims to provide a method and apparatus for manufacturing a nonwoven fabric that allows easy recovery of the nonwoven fabric, and the nonwoven fabric.

In order to solve the above problems, the inventors conducted extensive research and discovered that a nonwoven fabric can be produced by using two types of liquid that can form an interface with each other, applying a potential difference between an electrostatic spinning nozzle placed in the first liquid and a counter electrode connected to the second liquid, and then electrostatically spinning a liquid sample containing a fiber material from the electrostatic spinning nozzle toward the second liquid, and that the nonwoven fabric accumulates at the interface, thus completing the present invention.

That is, the present invention includes the following configurations:

＜1＞
A method for producing a nonwoven fabric, comprising: a potential difference forming step of applying a potential difference between an electrostatic spinning nozzle disposed in a first liquid and a counter electrode connected to a second liquid; and an electrostatic spinning step of electrostatically spinning a liquid sample containing a fiber material from the electrostatic spinning nozzle toward the second liquid by the potential difference, wherein the first liquid and the second liquid are solutions capable of forming an interface with each other.

In the above configuration, a liquid sample containing a fiber material is electrospun from the electrospinning nozzle disposed in the first liquid toward the second liquid by a potential difference applied between the electrospinning nozzle and the counter electrode (more specifically, between the electrospinning nozzle and the second liquid connected to the counter electrode). In the process in which the liquid sample passes through the first liquid, the solvent of the liquid sample is, for example, diffused or dissolved into the first liquid, and the solvent is removed from the liquid sample. As a result, the concentration of the fiber material, which is a solute, increases, and the fiber materials become entangled with each other, forming a raw material for forming a nonwoven fabric. The raw material moves from the first liquid toward the second liquid, similar to the liquid sample. At this time, an interface is formed between the first liquid and the second liquid. At the interface, forces such as surface tension, buoyancy, and/or electrical attraction act on the raw material, and as a result, the raw material remains at the interface. At the interface, the retained raw material is accumulated, and as a result, a nonwoven fabric is produced by the raw material.

＜2＞
The method for producing a nonwoven fabric according to <1>, further comprising a recovery step of recovering the nonwoven fabric accumulated at the interface after the electrostatic spinning step and/or simultaneously with the electrostatic spinning step.

With the above configuration, nonwoven fabric can be produced continuously. For example, if the recovery process is performed after the electrospinning process, a nonwoven fabric according to the size of the interface can be produced and recovered, and then the interface can be used to produce a nonwoven fabric again. On the other hand, if the recovery process is performed simultaneously with the electrospinning process, nonwoven fabric is produced at one end of the nonwoven fabric being recovered at the same time as it is recovered. In other words, a newly produced nonwoven fabric is bonded to one end of the nonwoven fabric being recovered. As a result, with this configuration, long nonwoven fabric can be produced without being limited by the size of the interface.

＜3＞
The method for producing a nonwoven fabric according to <1> or <2>, further comprising an interface shape control step of controlling a shape of an interface between the first liquid and the second liquid.

The shape of the interface between the first liquid and the second liquid can be easily controlled by ultrasonic waves (e.g., standing waves) or the like. Furthermore, it can be precisely controlled. With the above configuration, by controlling the shape of the interface, the shape of the nonwoven fabric produced at the interface can be easily controlled. Furthermore, it can be precisely controlled.

＜4＞
The method for producing a nonwoven fabric according to any one of <1> to <3>, further comprising a potential difference adjusting step of adjusting the magnitude of the potential difference.

With the above configuration, it is possible to control the structure of the nonwoven fabric (e.g., the thickness of the fibers that make up the nonwoven fabric, the density of the fibers that make up the nonwoven fabric, the degree of adhesion between the fibers that make up the nonwoven fabric, etc.).

＜5＞
The method for producing a nonwoven fabric according to any one of <1> to <4>, further comprising a spinning distance adjusting step of adjusting the distance between the electrostatic spinning nozzle and the interface.

With the above configuration, it is possible to control the structure of the nonwoven fabric (e.g., the thickness of the fibers that make up the nonwoven fabric, the density of the fibers that make up the nonwoven fabric, the degree of adhesion between the fibers that make up the nonwoven fabric, etc.).

＜6＞
The method for producing a nonwoven fabric according to any one of <1> to <5>, further comprising a solution discharging step of discharging a part of the first liquid.

As the liquid sample passes through the first liquid, the solvent of the liquid sample is, for example, diffused or dissolved into the first liquid. As a result, the solvent accumulates in the first liquid, and the amount of the first liquid increases, as does the concentration of the solvent in the first liquid. With the above configuration, the amount of the first liquid can be kept constant, and the solvent concentration in the first liquid can be kept low.

＜７＞
<6> A nonwoven fabric produced by the method according to any one of <1> to <6>.

With the above configuration, it is possible to provide nonwoven fabrics with a variety of properties.

＜8＞
A nonwoven fabric manufacturing apparatus comprising: a container for containing a first liquid and a second liquid that forms an interface between the first liquid and the first liquid; an electrostatic spinning nozzle disposed in a region of the container in which the first liquid is contained; and a counter electrode connected to a region of the container in which the second liquid is contained, wherein the electrostatic spinning nozzle electrostatically spins a liquid sample containing a fiber material toward the second liquid, and a potential difference is applied between the electrostatic spinning nozzle and the counter electrode.

In the above configuration, a liquid sample containing a fiber material is electrospun from the electrospinning nozzle disposed in the first liquid toward the second liquid by a potential difference applied between the electrospinning nozzle and the counter electrode (more specifically, between the electrospinning nozzle and the second liquid connected to the counter electrode). In the process in which the liquid sample passes through the first liquid, the solvent of the liquid sample is, for example, diffused or dissolved into the first liquid, and the solvent is removed from the liquid sample. As a result, the concentration of the fiber material, which is a solute, increases, and the fiber materials become entangled with each other, forming a raw material for forming a nonwoven fabric. The raw material moves from the first liquid toward the second liquid, similar to the liquid sample. At this time, an interface is formed between the first liquid and the second liquid. At the interface, forces such as surface tension, buoyancy, and/or electrical attraction act on the raw material, and as a result, the raw material remains at the interface. At the interface, the retained raw material is accumulated, and as a result, a nonwoven fabric is produced by the raw material.

According to one aspect of the present invention, it is possible to provide a method for manufacturing a nonwoven fabric, an apparatus for manufacturing a nonwoven fabric, and a nonwoven fabric that allows easy recovery of the nonwoven fabric.

FIG. 1 is a schematic diagram illustrating a manufacturing apparatus according to an embodiment of the present invention. 1 is a schematic diagram showing a manufacturing apparatus according to an embodiment of the present invention and an interface within the manufacturing apparatus; 1 is a flow chart of a manufacturing method according to an embodiment of the present invention. 1 is an external view and an SEM image of a nonwoven fabric of the present invention. 1 is a SEM image of a nonwoven fabric of the present invention. 1 is a SEM image of a nonwoven fabric of the present invention. 1 is a SEM image of a nonwoven fabric of the present invention.

One embodiment of the present invention is described below, but the present invention is not limited to this. The present invention is not limited to each of the configurations described below, and various modifications are possible within the scope of the claims. The technical scope of the present invention also includes embodiments and examples obtained by appropriately combining the technical means disclosed in different embodiments and examples. In addition, all documents described in this specification are incorporated herein by reference. In this specification, when a numerical range is described as "A to B," the description intends "greater than or equal to A and less than or equal to B."

1. Method for producing nonwoven fabric
First, a method for producing a nonwoven fabric according to one embodiment of the present invention will be described with reference to FIG.

A method for producing a nonwoven fabric according to one embodiment of the present invention (301) includes a potential difference forming step S1 in which a potential difference is applied between an electrostatic spinning nozzle disposed in a first liquid and a counter electrode connected to a second liquid, and an electrostatic spinning step S2 in which a liquid sample containing a fiber material is electrostatically spun from the electrostatic spinning nozzle toward the second liquid by the potential difference, the first liquid and the second liquid being liquids capable of forming an interface with each other.

In the above configuration, a liquid sample containing a fiber material is electrospun from the electrospinning nozzle disposed in the first liquid toward the second liquid by a potential difference applied between the electrospinning nozzle and the counter electrode (more specifically, between the electrospinning nozzle and the second liquid connected to the counter electrode). In the process in which the liquid sample passes through the first liquid, the solvent of the liquid sample is, for example, diffused or dissolved into the first liquid, and the solvent is removed from the liquid sample. As a result, the concentration of the fiber material, which is a solute, increases, and the fiber materials become entangled with each other, forming a raw material for forming a nonwoven fabric. In addition, the raw material moves from the first liquid toward the second liquid, similar to the liquid sample. At this time, an interface is formed between the first liquid and the second liquid. At the interface, forces such as surface tension, buoyancy, and/or electrical attraction act on the raw material, and as a result, the raw material remains at the interface. After that, the retained raw material is accumulated at the interface, and as a result, a nonwoven fabric is produced by the raw material.

As described above, in the present invention, a nonwoven fabric is produced using an interface that does not form a strong bond with the nonwoven fabric, and therefore the present invention has the advantage that the nonwoven fabric can be easily recovered. Furthermore, in the present invention, an operation of peeling the nonwoven fabric from a collector or the like is not required, and therefore the present invention has the advantage that damage to the nonwoven fabric that occurs during said operation can be avoided. Furthermore, in the present invention, a nonwoven fabric is produced using an interface whose size and/or shape can be easily adjusted, and therefore the present invention has the advantage that a nonwoven fabric of a desired size (e.g., a large nonwoven fabric) and/or a nonwoven fabric of a desired shape can be easily produced.

In this specification, "electrospinning" means spraying a liquid sample to which a voltage has been applied from an electrospinning nozzle, passing the liquid through the first liquid, and then producing a nonwoven fabric at the interface.

In this specification, "liquid sample" means a liquid in which fiber material is dissolved in a solvent.

The concentration of the fiber material in the liquid sample is not limited and can be set appropriately depending on the type of fiber material and the type of solvent. When the entire liquid sample is taken as 100 wt%, the concentration of the fiber material in the liquid sample is, for example, preferably 1 wt% to 50 wt%, more preferably 5 wt% to 50 wt%, more preferably 10 wt% to 25 wt%, more preferably 10 wt% to 20 wt%, and even more preferably 10 wt% to 15 wt%.

Examples of compounds used as the fiber material include polymeric compounds. Examples of polymeric compounds include cellulose or its derivatives (such as acetyl cellulose), polyvinyl alcohol or its derivatives (such as polyvinyl butyral), polyacrylonitrile, polyacrylic acid, polyvinylidene fluoride, polyethylene oxide, polyester, polyvinylpyrrolidone, ethylene-vinyl alcohol copolymer, butadiene rubber, polyurethane, and biodegradable plastics (such as polylactic acid and polyhydroxyalkanoate). Of the above polymeric compounds, acetyl cellulose and polyvinyl alcohol are preferred because of their advantage of high reactivity. These polymeric compounds can be used alone or in combination of two or more.

In the method for producing a nonwoven fabric according to one embodiment of the present invention, two different types of liquids, a first liquid and a second liquid, are used. In this case, the surface of the nonwoven fabric that comes into contact with the first liquid tends to have, for example, (i) a polymer compound that has a high affinity with the first liquid among the multiple types of polymer compounds that make up the fiber material, or (ii) an intramolecular region of one or more polymer compounds that make up the fiber material and has a high affinity with the first liquid. On the other hand, the surface of the nonwoven fabric that comes into contact with the second liquid tends to have, for example, (iii) a polymer compound that has a high affinity with the second liquid among the multiple types of polymer compounds that make up the fiber material, or (iv) an intramolecular region of one type of polymer compound that makes up the fiber material and has a high affinity with the second liquid. As a result, with the method for producing a nonwoven fabric according to one embodiment of the present invention, a nonwoven fabric in which the properties of the surface of the nonwoven fabric that comes into contact with the first liquid and the surface of the nonwoven fabric that comes into contact with the second liquid are different can be easily produced. For example, if a liquid with low polarity is used as the first liquid and a liquid with high polarity is used as the second liquid, a nonwoven fabric with two sides with different water repellency can be produced.

The solvent of the liquid sample is not particularly limited as long as it can dissolve the fiber material, and examples of the solvent include water, alcohol (e.g., methanol, ethanol, propanol), N,N-dimethylformamide (DMF), acetone, N,N-dimethylacetamide (DMAc), acetic acid, dimethylsulfoxide (DMSO), and halogenated hydrocarbons (e.g., chloroform). From the viewpoint of producing a nonwoven fabric with a more clearly defined fiber form, N,N-dimethylformamide, acetone, DMSO, and the like are preferred. These solvents can be used alone or in combination of two or more types. In addition, electrolytes, organometallic compounds, or functional compounds (inorganic fine particles, biocatalysts, etc.) may be dissolved or dispersed in the solvent as appropriate.

The positional relationship between the first liquid and the second liquid is not particularly limited as long as it is possible to form a nonwoven fabric. That is, the second liquid may be disposed on the first liquid, or the first liquid may be disposed on the second liquid. In other words, in the present invention, a liquid sample may be electrostatically spun from the first liquid disposed on the upper side toward the second liquid disposed on the lower side, or from the first liquid disposed on the lower side toward the second liquid disposed on the upper side. The positional relationship between the first liquid and the second liquid may be determined, for example, by the magnitude relationship between the specific gravity of the first liquid and the specific gravity of the second liquid.

The first liquid and the second liquid may be liquids capable of forming an interface with each other, and the specific configuration is not limited.

For example, the first liquid in which the electrostatic spinning nozzle is placed may have a lower dielectric constant than the second liquid connected to the counter electrode. With this configuration, a desired potential difference can be easily formed between the electrostatic spinning nozzle and the counter electrode. As a result, a liquid sample containing a fiber material can be efficiently electrostatically spun from the electrostatic spinning nozzle toward the second liquid.

For example, the dielectric constant A of the first liquid and the dielectric constant B of the second liquid may satisfy the relationship "A<B", may satisfy the relationship "A<(9/10)×B", may satisfy the relationship "A<(8/10)×B", may satisfy the relationship "A<(7/10)×B", may satisfy the relationship "A<(6/10)×B", may satisfy the relationship "A<(5/10)×B", may satisfy the relationship "A<(4/10)×B", may satisfy the relationship "A<(3/10)×B", may satisfy the relationship "A<(2/10)×B", or may satisfy the relationship "A<(1/10)×B".

The first liquid may have a small dielectric constant. For example, the dielectric constant of the first liquid is preferably 25 or less, more preferably 20 or less, more preferably 15 or less, more preferably 10 or less, and most preferably 5 or less. The lower limit of the dielectric constant of the first liquid is not limited and may be, for example, 0.1 or 1. With this configuration, a desired potential difference can be easily formed between the electrostatic spinning nozzle and the opposing electrode. As a result, a liquid sample containing a fiber material can be efficiently electrostatically spun from the electrostatic spinning nozzle toward the second liquid.

Specific examples of the first liquid include hydrocarbons (e.g., hexane, heptane, pentane, decane, dodecane, toluene, liquid paraffin, IP solvent), alcohols (e.g., butanol, pentanol, octanol), halogenated hydrocarbons (e.g., benzyl chloride, chloroform, chlorooctane, carbon tetrachloride, perfluorohexane), and dioxane. From the viewpoint of versatility, hexane, toluene, and IP solvent are preferred among the above first liquids. These liquids can be used alone or in combination of two or more types.

The second liquid may have a large relative dielectric constant. For example, the relative dielectric constant of the second liquid is preferably greater than 25, more preferably greater than 30, more preferably greater than 40, more preferably greater than 50, more preferably greater than 60, more preferably greater than 70, and most preferably greater than 80. The upper limit of the relative dielectric constant of the second liquid is not limited and may be, for example, 150 or 100. With this configuration, a desired potential difference can be easily formed between the electrostatic spinning nozzle and the opposing electrode. As a result, a liquid sample containing a fiber material can be efficiently electrostatically spun from the electrostatic spinning nozzle toward the second liquid.

Specific examples of the second liquid include water, acetone, alcohol (e.g., methanol, ethanol), glycol (e.g., ethylene glycol, propylene glycol), acid (e.g., acetic acid, formic acid), dimethylformamide, dimethylsulfoxide, and solutions using these as solvents. From the viewpoint of versatility, water, alcohol, and dimethylsulfoxide are preferred among the above second liquids. These liquids can be used alone or in combination of two or more.

In the potential difference forming step S1, the potential difference applied between the electrostatic spinning nozzle and the counter electrode is not particularly limited as long as it is possible to produce a nonwoven fabric, and can be set appropriately depending on the type of the first liquid, the type of the second liquid, and the distance between the electrostatic spinning nozzle and the counter electrode. The potential difference is, for example, preferably 1 kv to 100 kv, more preferably 5 kv to 50 kv, more preferably 10 kv to 40 kv, more preferably 12 kV to 36 kV, more preferably 12 kV to 24 kV, and most preferably 20 to 24 kV. If the applied voltage is within the above range, the nonwoven fabric will easily form a fiber shape.

The electrostatic spinning nozzle and counter electrode can be commercially available as appropriate. The nonwoven fabric manufacturing device will be described later.

As shown in FIG. 3, the method 303 for producing a nonwoven fabric according to one embodiment of the present invention may include a recovery step S3 for recovering the nonwoven fabric accumulated at the interface after the electrostatic spinning step S2 and/or simultaneously with the electrostatic spinning step S2. The recovery step S3 may be performed by a recovery section provided in the nonwoven fabric production apparatus described below.

With the above configuration, nonwoven fabric can be continuously manufactured. For example, if the recovery step S3 is performed after the electrostatic spinning step S2, a nonwoven fabric according to the size of the interface can be manufactured and recovered, and then the interface can be used to manufacture a nonwoven fabric again. On the other hand, if the recovery step S3 is performed simultaneously with the electrostatic spinning step S2, nonwoven fabric is manufactured at one end of the nonwoven fabric being recovered at the same time as it is recovered. In other words, a newly manufactured nonwoven fabric is bonded to one end of the nonwoven fabric being recovered. As a result, with this configuration, a large nonwoven fabric (in other words, a long nonwoven fabric) can be manufactured without being limited by the size of the interface.

As shown in FIG. 3, the nonwoven fabric manufacturing method 303 according to one embodiment of the present invention may further include an interface shape control step S0 for controlling the shape of the interface between the first liquid and the second liquid. The interface shape control step S0 may be performed, for example, before the potential difference formation step S1. The interface shape control step S0 may be performed by an interface shape control unit provided in the nonwoven fabric manufacturing apparatus described below.

The shape of the interface between the first liquid and the second liquid can be easily controlled by ultrasonic waves (e.g., standing waves) or the like. Furthermore, it can be precisely controlled. With the above configuration, by controlling the shape of the interface, the shape of the nonwoven fabric produced at the interface can be easily controlled. Furthermore, it can be precisely controlled.

Interface control 202 in FIG. 2 shows an example of a method of controlling the interface shape by the interface shape control unit 5. The interface shape control unit 5 can be a unit that changes the interface 12 into a desired shape by, for example, emitting ultrasonic waves (e.g., standing waves). In addition to ultrasonic waves, other methods that can change the shape of the interface 12 include, for example, electromagnetic waves, control of the flow rate of the liquid parallel to the interface (Karman vortex), and local temperature control of the interface. By electrostatically spinning a liquid sample onto the interface 12 whose shape has been changed, a nonwoven fabric 20 having a shape that matches the shape of the interface 12 can be obtained.

The shape of the interface 12 is not particularly limited, and examples include wavy, crepe, and spiral shapes. From the viewpoint of enabling the manufactured nonwoven fabric to be suitably used for applications such as household goods, it is preferable that the shape of the interface 12 is wavy or crepe.

As shown in FIG. 3, the method 302 for producing a nonwoven fabric according to one embodiment of the present invention may further include a potential difference adjustment step S1a for adjusting the magnitude of the potential difference. The potential difference adjustment step S1a may be performed, for example, before the potential difference formation step S1. The potential difference adjustment step S1a may be performed by a potential difference adjustment unit provided in the nonwoven fabric production apparatus described below.

With the above configuration, the structure of the nonwoven fabric (e.g., the thickness of the fibers that make up the nonwoven fabric, the density of the fibers that make up the nonwoven fabric, the degree of adhesion between the fibers that make up the nonwoven fabric, etc.) can be controlled by adjusting the magnitude of the potential difference.

In the manufacturing method 302 for a nonwoven fabric according to one embodiment of the present invention, for example, (i) the potential difference adjustment step S1a may be performed followed by the potential difference formation step S1, (ii) the potential difference adjustment step S1a may be performed followed by the spinning distance adjustment step S1b described later, and then the potential difference formation step S1 may be performed, or (ii) the potential difference adjustment step S1a and the spinning distance adjustment step S1b described later may be performed a desired number of times followed by the potential difference formation step S1. In addition, the potential difference adjustment step S1a and the spinning distance adjustment step S1b described later may be performed as a single step or as separate steps.

In the potential difference adjustment step S1a, the potential difference can be adjusted appropriately depending on the type of the first liquid, the type of the second liquid, and the distance between the electrostatic spinning nozzle and the opposing electrode. The potential difference is, for example, preferably 1 kv to 100 kv, more preferably 5 kv to 50 kv, more preferably 10 kv to 40 kv, more preferably 12 kV to 36 kV, more preferably 12 kV to 24 kV, and most preferably 20 to 24 kV.

As shown in FIG. 3, the nonwoven fabric manufacturing method 302 according to one embodiment of the present invention may further include a spinning distance adjustment step S1b for adjusting the distance between the electrostatic spinning nozzle and the interface. The spinning distance adjustment step S1b may be performed, for example, before the potential difference formation step S1. The spinning distance adjustment step S1b may be performed by a spinning distance adjustment unit provided in the nonwoven fabric manufacturing apparatus described later.

With the above configuration, it is possible to control the structure of the nonwoven fabric (e.g., the thickness of the fibers constituting the nonwoven fabric, the density of the fibers constituting the nonwoven fabric, the degree of adhesion between the fibers constituting the nonwoven fabric, etc.). For example, as the distance between the electrostatic spinning nozzle and the interface becomes closer, the fiber diameter tends to become thicker, and conversely, as the distance becomes farther, the fiber diameter tends to become thinner and the fiber shape tends to become more clearly defined.

In the manufacturing method 302 for manufacturing a nonwoven fabric according to one embodiment of the present invention, for example, (i) the potential difference forming step S1 may be performed after the spinning distance adjusting step S1b, (ii) the above-mentioned potential difference adjusting step S1a may be performed after the spinning distance adjusting step S1b, and then the potential difference forming step S1 may be performed, or (ii) the potential difference forming step S1 may be performed after the spinning distance adjusting step S1b and the above-mentioned potential difference adjusting step S1a are performed a desired number of times. In addition, the potential difference adjusting step S1a and the spinning distance adjusting step S1b described later may be performed as one step or as separate steps.

The distance between the electrospinning nozzle and the interface can be set appropriately depending on the type of the first liquid, the type of the second liquid, and the potential difference between the electrospinning nozzle and the counter electrode. The distance is preferably 1.0 cm or more, more preferably 2.0 cm or more, more preferably 3.0 cm or more, and even more preferably 4.0 cm or more. The upper limit of the distance is not limited and may be, for example, 100 cm, 50 cm, or 10 cm.

In the spinning distance adjustment step S1b, the distance between the electrostatic spinning nozzle and the interface may be adjusted by moving either the electrostatic spinning nozzle or the interface, or both.

As shown in FIG. 3, the nonwoven fabric manufacturing method 303 according to one embodiment of the present invention may further include a liquid discharge step S4 of discharging a portion of the first liquid (e.g., discharging a portion of the first liquid from a container described below). The liquid discharge step S4 may be performed, for example, after the recovery step S3. The liquid discharge step S4 may be performed by a discharge port provided in the nonwoven fabric manufacturing apparatus described below.

As the liquid sample passes through the first liquid, the solvent of the liquid sample is, for example, diffused or dissolved into the first liquid. As a result, the solvent accumulates in the first liquid, and the amount of the first liquid increases, as does the concentration of the solvent in the first liquid. With the above configuration, the amount of the first liquid can be kept constant, and the solvent concentration in the first liquid can be kept low.

The nonwoven fabric manufacturing method 303 according to one embodiment of the present invention may further include a liquid introduction step of introducing new first liquid (e.g., introducing new first liquid into a container described below). The liquid introduction step may be performed, for example, simultaneously with the liquid discharge step S4. In this case, the liquid introduction step may be included in the liquid discharge step S4. The liquid discharge step S4 may be performed by an inlet provided in the nonwoven fabric manufacturing device. With this configuration, the amount of the first liquid can be kept more constant, and the solvent concentration in the first liquid can be kept lower.

[2. Nonwoven fabric manufacturing equipment]
An outline of a nonwoven fabric manufacturing apparatus according to one embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 illustrates a schematic structure of an example of a nonwoven fabric manufacturing apparatus 101. Items already explained in [1. Nonwoven fabric manufacturing method] will not be explained below.

The nonwoven fabric manufacturing apparatus 101 includes a container 1 that contains a first liquid 10 and a second liquid 11 that forms an interface 12 between the first liquid 10 and the first liquid 10, an electrostatic spinning nozzle 2 that is disposed in the area of the container 1 where the first liquid 10 is contained, and a counter electrode 3 that is connected to the area of the container 1 where the second liquid 11 is contained. The electrostatic spinning nozzle 2 electrostatically spins a liquid sample 13 containing a fiber material toward the second liquid 11, and a potential difference is applied between the electrostatic spinning nozzle 2 and the counter electrode 3.

In the above configuration, a liquid sample 13 containing a fiber material is electrospun from the electrospinning nozzle 2 disposed in the first liquid 10 toward the second liquid 11 by a potential difference applied between the electrospinning nozzle 2 and the counter electrode 3 (more specifically, between the electrospinning nozzle 2 and the second liquid 11 connected to the counter electrode 3). In the process of the liquid sample passing through the first liquid, the solvent of the liquid sample is, for example, diffused or dissolved into the first liquid, and the solvent is removed from the liquid sample. As a result, the concentration of the fiber material, which is a solute, increases and the fiber materials become entangled with each other, forming the raw material 21 for forming the nonwoven fabric. In addition, the raw material 21 moves from the first liquid 10 toward the second liquid 11, similar to the liquid sample 13. At this time, an interface 12 is formed between the first liquid 10 and the second liquid 11. At the interface 12, forces such as surface tension, buoyancy, and/or electrical attraction act on the raw material 21, causing the raw material 21 to remain at the interface 12. The remaining raw material 21 then accumulates at the interface 12, resulting in the nonwoven fabric 20 being produced by the raw material 21.

The electrostatic spinning nozzle 2 is not particularly limited as long as it can apply a voltage to the liquid sample 13. Examples of the electrostatic spinning nozzle 2 include a metal tube (e.g., stainless steel), a capillary tube with a metal-plated surface, a syringe, a needle, and the like. A syringe is preferred from the viewpoint of making it easier to adjust the amount of spinning of the liquid sample 13. It is also possible to insert an electrode directly into the liquid sample 13 and apply a high voltage. In this case, the material of the nozzle 2 is not limited.

The number of electrostatic spinning nozzles 2 provided in one nonwoven fabric manufacturing apparatus 101 is not limited, and may be one or more (e.g., two or more, three or more, four or more, five or more). The number of electrostatic spinning nozzles 2 provided in one nonwoven fabric manufacturing apparatus 101 may be appropriately set according to the size of the container 1. For example, if the container 1 is large, the number of electrostatic spinning nozzles 2 provided in one nonwoven fabric manufacturing apparatus 101 may be multiple. With this configuration, it is possible to easily manufacture a large nonwoven fabric having substantially the same properties (e.g., thickness) throughout the entire nonwoven fabric.

The counter electrode 3 provided in the second solution 11 may be any electrode capable of forming a potential difference between itself and the electrostatic spinning nozzle 2, and its shape and material are not particularly limited. The shape of the counter electrode 3 may be, for example, a ring, a plate, a mesh, a rod, a woven fabric, a nonwoven fabric, or the like. A plurality of plate-shaped or rod-shaped electrodes may also be arranged. The material of the counter electrode 3 may be, for example, a metal such as stainless steel, platinum, aluminum, or copper. The second liquid 11 (for example, a liquid having a large relative dielectric constant such as water) itself may be used as an electrode. For example, the second solution 11 may function as a counter electrode by connecting an earthed copper wire or the like to the second solution 11.

The volume and shape of the container 1 are not limited. By appropriately selecting the volume and shape of the container 1, the width and/or shape of the interface 12 can be adjusted. As a result, the width and/or shape of the nonwoven fabric 20 produced can be easily adjusted.

As shown in FIG. 2, the nonwoven fabric manufacturing apparatus 201 according to one embodiment of the present invention may include a recovery section 4 for recovering the produced nonwoven fabric.

The recovery unit 4 may be any device capable of recovering the produced nonwoven fabric, and its configuration is not limited. The recovery unit 4 may be, for example, (i) a rotary collector that winds up the nonwoven fabric formed at the interface, (ii) a net that picks up the nonwoven fabric formed at the interface, (iii) a heater that dries the nonwoven fabric, or (iv) a liquid recovery system. From the viewpoint of being able to continuously recover a large amount of nonwoven fabric, it is preferable that the recovery unit 4 be a rotary collector (rotary drum).

As shown in FIG. 2, the nonwoven fabric manufacturing apparatus 201 according to one embodiment of the present invention may include an interface shape control unit 5 that controls the shape of the interface.

The interface shape control unit 5 may be any device capable of controlling the shape of the interface, and its configuration is not limited. The interface shape control unit 5 may be, for example, (i) an ultrasonic irradiation device, (ii) an electromagnetic wave generator, or (iii) a Karman vortex generator. From the viewpoint of being able to easily control the shape of the interface, it is preferable that the interface shape control unit 5 is an ultrasonic irradiation device.

As shown in FIG. 2, the nonwoven fabric manufacturing apparatus 201 according to one embodiment of the present invention may be equipped with a potential difference adjustment unit 6 that adjusts the magnitude of the potential difference.

The potential difference adjustment unit 6 may be configured in any way as long as it can adjust the potential difference between the electrostatic spinning nozzle and the opposing electrode.

The potential difference adjustment unit 6 may be a commercially available device capable of adjusting the voltage applied to the electrostatic spinning nozzle. The potential difference adjustment unit 6 may also be integrated with the electrostatic spinning nozzle.

As shown in FIG. 2, the nonwoven fabric manufacturing apparatus 201 according to one embodiment of the present invention may be equipped with a spinning distance adjustment unit 7 that adjusts the distance between the electrostatic spinning nozzle and the interface.

The spinning distance adjustment unit 7 may be configured in any way as long as it can adjust the distance between the electrostatic spinning nozzle and the interface.

As shown in FIG. 2, the spinning distance adjustment unit 7 may change the position of the electrostatic spinning nozzle from position A to position B and/or from position B to position A.

In this case, the spinning distance adjustment unit 7 may (i) change the position of the electrostatic spinning nozzle from position A to position B and/or from position B to position A by moving the electrostatic spinning nozzle, or (ii) change the position of the electrostatic spinning nozzle from position A to position B and/or from position B to position A by moving the container. Note that a commercially available device may be used as appropriate as a device for moving the electrostatic spinning nozzle or the container.

Another embodiment of the spinning distance adjustment unit 7 is to provide multiple electrostatic spinning nozzles at different distances from the interface in advance, and to select the electrostatic spinning nozzle to be driven as appropriate. For example, electrostatic spinning nozzle A is provided in advance at position A, and electrostatic spinning nozzle B is provided in advance at position B. By driving either electrostatic spinning nozzle A or electrostatic spinning nozzle B, the distance between the electrostatic spinning nozzle and the interface can be adjusted.

Another embodiment of the spinning distance adjustment unit 7 is to provide the container with multiple insertion ports at different distances from the interface, and to select the insertion port into which the electrostatic spinning nozzle is to be inserted as appropriate. An insertion port A located at position A and an insertion port B located at position B are provided in the container in advance. After inserting the electrostatic spinning nozzle into either insertion port A or insertion port B, the distance between the electrostatic spinning nozzle and the interface can be adjusted by driving the electrostatic spinning nozzle.

As shown in FIG. 2, the nonwoven fabric manufacturing apparatus 201 according to one embodiment of the present invention may include an outlet 30 for discharging a portion of the first liquid contained in the container to the outside of the container.

The outlet 30 is not particularly limited as long as it is capable of discharging the desired liquid. For example, it may be equipped with a circulation mechanism such as a pump, or may simply be equipped with an opening that can be opened and closed.

The nonwoven fabric manufacturing apparatus 201 according to one embodiment of the present invention may be provided with an inlet for introducing new first liquid into the container. The inlet may be provided, for example, in an area of the container where the first liquid is stored (for example, an area facing the discharge outlet 30).

The inlet is not particularly limited as long as it is capable of introducing the desired liquid. For example, it may be equipped with a circulation mechanism such as a pump, or may simply be equipped with an opening that can be opened and closed.

The nonwoven fabric manufacturing apparatus according to one embodiment of the present invention preferably has the following configuration:
(1) The nonwoven fabric manufacturing apparatus further includes a recovery section for recovering the nonwoven fabric accumulated at the interface.
(2) The nonwoven fabric manufacturing apparatus further includes an interface shape control unit that controls the shape of the interface.
(3) The nonwoven fabric manufacturing apparatus further includes a potential difference adjusting unit that adjusts the magnitude of the potential difference.
(4) The nonwoven fabric manufacturing apparatus further includes a spinning distance adjustment unit that adjusts the distance between the electrostatic spinning nozzle and the interface.
(5) The nonwoven fabric manufacturing apparatus further includes a discharge port for discharging a portion of the first liquid contained in the container to the outside of the container.

[3. Nonwoven Fabric]
The nonwoven fabric according to one embodiment of the present invention is produced by the production method according to one embodiment of the present invention.

It is impossible or impractical to directly identify the nonwoven fabric by its structure or properties. In light of the differences in structure and associated properties of each of the fiber materials used, it is impossible to directly identify the nonwoven fabric produced by the manufacturing method of the nonwoven fabric of the present invention by its structure or properties.

In the method for producing a nonwoven fabric according to one embodiment of the present invention, two different liquids, a first liquid and a second liquid, are used. In this case, the surface of the nonwoven fabric that comes into contact with the first liquid tends to have, for example, (i) a polymer compound that has a high affinity with the first liquid among the multiple polymer compounds that make up the fiber material, or (ii) an intramolecular region of one or more polymer compounds that make up the fiber material and has a high affinity with the first liquid. On the other hand, the surface of the nonwoven fabric that comes into contact with the second liquid tends to have, for example, (iii) a polymer compound that has a high affinity with the second liquid among the multiple polymer compounds that make up the fiber material, or (iv) an intramolecular region of one type of polymer compound that makes up the fiber material and has a high affinity with the second liquid. As a result, the method for producing a nonwoven fabric according to one embodiment of the present invention makes it possible to easily produce a nonwoven fabric in which the properties of the surface of the nonwoven fabric that comes into contact with the first liquid and the surface of the nonwoven fabric that comes into contact with the second liquid are different.

Examples of such nonwoven fabrics include (i) nonwoven fabrics whose front surface is hydrophilic and whose back surface is water-repellent, (ii) nonwoven fabrics whose fiber material has different degrees of crystallinity on the front and back surfaces, (iii) nonwoven fabrics whose fiber surface structures (smoothness, porosity, etc.) are different on the front and back surfaces, and (iv) nonwoven fabrics whose interfacial gaps between fibers are different on the front and back surfaces.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[Test 1]
Using the nonwoven fabric manufacturing apparatus 101 shown in FIG. 1, the first liquid was hexane, the second liquid was water, and electrostatic spinning of the nonwoven fabric was performed. The liquid sample was 2 mL of a 10 wt% CA-DMAc solution obtained by mixing 1 g of cellulose acetate (CA) (manufactured by Wako Pure Chemical Industries, Ltd.) and 9 g of N,N-dimethylacetamide (DMAc) (manufactured by Nacalai Tesque, Inc.). The spinning conditions were a supply rate of the liquid sample to the electrostatic spinning nozzle of 0.6 mL/h, an applied voltage to the electrostatic spinning nozzle of 20 kV, and a distance between the interface and the electrostatic spinning nozzle of 2.5 cm. In addition, a copper wire grounded to the ground was used as the counter electrode. An external view and an SEM image of the obtained nonwoven fabric are shown in FIG. 4.

Figure 4 shows that a nonwoven fabric was formed at the interface between hexane and water. This indicates that the water surface acted as a collector.

[Test 2]
A nonwoven fabric was produced in the same manner as in Test 1 except that the applied voltage was changed. SEM images of the obtained nonwoven fabric are shown in Figure 5. The applied voltages to the electrostatic spinning nozzle were (a) 12 kV, (b) 16 kV, (c) 20 kV, and (d) 24 kV, respectively. SEM images of the obtained nonwoven fabric are shown in Figure 5.

Figure 5 shows that the nonwoven fabric produced with an applied voltage of 24 kV had the most fibrous shape. Therefore, an applied voltage of 24 kV was shown to be the most favorable for forming a fibrous shape.

[Test 3]
A nonwoven fabric was produced in the same manner as in Test 1, except that the distance between the interface and the electrostatic spinning nozzle was changed. The distances were (a) 3.0 cm, (b) 3.5 cm, and (c) 4.0 cm. SEM images of the obtained nonwoven fabric are shown in FIG. 6.

Figure 6 shows that (c) has the most fibrous shape. This shows that the greater the distance between the interface and the needle, the easier it is to form a fibrous shape.

[Test 4]
Nonwoven fabrics were prepared in the same manner as in Example 1, except that the material of the liquid sample was changed from cellulose acetate to polyvinylidene fluoride (PVDF). The nonwoven fabrics obtained were subjected to different treatments. The nonwoven fabrics were each subjected to the following treatments: (a) air drying, (b) immersion in ethanol, and (c) immersion in distilled water. SEM images of the nonwoven fabrics after the treatments are shown in FIG. 7.

From Figure 7, it was found that fibers can be formed using PVDF. Also, _a1 , _b1 , and _c1 are SEM images of the sides that were in contact with hexane during preparation, and _a2 , _b2 , and _c2 are SEM images of the sides that were in contact with water. It can be seen that the shape of the fibers is different on each surface. This shows that it is possible to manufacture nonwoven fabrics with different properties on one side and the other side.

The present invention can be suitably used as a method for producing nonwoven fabric.

REFERENCE SIGNS LIST 1 Container 2 Electrostatic spinning nozzle 3 Counter electrode 4 Recovery section 5 Interface shape control section 6 Potential difference adjustment section 7 Spinning distance adjustment section 10 First liquid 11 Second liquid 12 Interface 13 Liquid sample 20 Nonwoven fabric 21 Raw material 30 Discharge port 101 Nonwoven fabric manufacturing apparatus 201 Nonwoven fabric manufacturing apparatus 301 Nonwoven fabric manufacturing method 302 Nonwoven fabric manufacturing method 303 Nonwoven fabric manufacturing method

Claims (7)

A potential difference forming step of applying a potential difference between an electrostatic spinning nozzle disposed in the first liquid and a counter electrode connected to the second liquid;
an electrostatic spinning step of electrostatically spinning a liquid sample including a fiber material from the electrostatic spinning nozzle toward the second liquid by the potential difference;
the first liquid and the second liquid are solutions capable of forming an interface with each other,
A method for producing a nonwoven fabric, wherein the first liquid and the second liquid have different specific gravities, and the dielectric constant of the first liquid is lower than the dielectric constant of the second liquid . The method for producing the nonwoven fabric according to claim 1 further comprises a recovery step of recovering the nonwoven fabric accumulated at the interface after and/or simultaneously with the electrostatic spinning step. The method for producing a nonwoven fabric according to claim 1 or 2, further comprising an interface shape control step for controlling the shape of the interface between the first liquid and the second liquid. The method for producing a nonwoven fabric according to any one of claims 1 to 3 further includes a potential difference adjustment step for adjusting the magnitude of the potential difference. The method for producing a nonwoven fabric according to any one of claims 1 to 4, further comprising a spinning distance adjustment step for adjusting the distance between the electrostatic spinning nozzle and the interface. The method for producing a nonwoven fabric according to any one of claims 1 to 5, further comprising a solution discharge step of discharging a portion of the first liquid. a container containing a first liquid and a second liquid forming an interface between the first liquid and the second liquid;
An electrostatic spinning nozzle disposed in a region of the container in which the first liquid is contained;
a counter electrode connected to a region of the container in which the second liquid is contained;
The electrostatic spinning nozzle electrostatically spins a liquid sample including a fiber material toward the second liquid,
A potential difference is applied between the electrospinning nozzle and a counter electrode ,
the first liquid and the second liquid are solutions capable of forming an interface with each other,
The first liquid and the second liquid have different specific gravities, and the dielectric constant of the first liquid is lower than the dielectric constant of the second liquid.
Nonwoven fabric manufacturing equipment.

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