Patent Application
20210025079
The present invention relates to an apparatus and a method for producing a nanofiber, which is capable of providing a high-quality nanofiber in a simple structure.
In recent years, demand of a nanofiber is rapidly increasing in accordance with expansion of use of a fiber having a nanometer-order diameter, namely a nanofiber. In accordance with expansion of use of the nanofiber, a special nanofiber has been required which is high in quality and corresponds to purpose. Regarding a nanofiber producing method, there are conventional methods such as an electrospinning method, a melt blown method or the like, and there are advantages and disadvantages with each method.
Patent Document 1 as the above-mentioned background of the invention discloses a method for producing a nonwoven fabric consisting of a plurality of kinds of fiber which is made by mixing a solution discharging fiber to a melt blown fiber. Specifically, by using a solution spinning unit which ejects a spinning solution discharged from a liquid discharge portion with a gas ejected from a gas discharge portion, the solution discharge fiber made by discharging and fiberizing the spinning solution is mixed into a fiber flow of a melt blown fiber delivered from a nozzle by the melt blown method.
Furthermore, Non-Patent Document 1 discloses a nanofiber producing method using an electrospinning method. A conventional electrospinning method for producing the nanofiber requires solvent for swelling resin, however, Non-Patent Document 1 discloses a configuration for preventing flashing and explosion caused by using a solvent by swelling by a heat without using the solvent. Additionally, disadvantages of the nanofiber producing method using the meld blown method are described in detail.
Non-Patent Literature 1: WEB-Journal No. 151 Nonwoven Fabric Extra Issue (http://www.webj.co.jp/index.html)
As described in the above-mentioned Non-Patent Literature 1, when a fiber diameter is reduced in the nanofiber producing method of the conventional melt blown method, it is considered to apply a method for ejecting high-temperature air at high speed and a method for suppressing discharge of polymer. When the high-temperature air is ejected at high speed, the fiber diameter is reduced but length of the fiber is shortened and shredded. On the other hand, when discharge of polymer is suppressed, an amount of production per unit time is extremely reduced. Accordingly, it is difficult for either method to achieve mass production of the nanofiber having a good quality. In an electrospinning method, productivity has been improved, however, an apparatus has become complicated, countermeasures is required for preventing flashing and explosion, and cost of manufacture has become expensive.
The present invention was made in consideration of the above problems, and an object of the present invention is to provide an apparatus and a method for producing a nanofiber which is capable of supplying a large amount of the nanofiber having good quality in nanofiber producing method of a melt blown method, and improving safety by eliminating factor of flashing and explosion.
According to the present invention, there is provided an apparatus for producing a nanofiber comprising a liquid raw material discharge unit for discharging a liquid raw material to a high-pressure gas flow ejected from a high-pressure gas ejection unit, wherein a plurality of the liquid raw material discharge units are provided around the high-pressure gas flow ejected from the high-pressure gas ejection unit.
According to the present invention, there is provided an apparatus for producing the nanofiber wherein the liquid raw material discharge unit comprises an extruding unit for melting and extruding a raw material.
According to the present invention, there is provided an apparatus for producing the nanofiber wherein the liquid raw material discharge unit comprises a unit for supplying a dissolved raw material.
According to the present invention, there is provided an apparatus for producing the nanofiber wherein the high-pressure gas ejection unit is provided with a gas supply unit for supplying a high-pressure and high-temperature gas, and the high-pressure gas ejection unit ejects the high-temperature gas at a high pressure.
According to the present invention, there is provided an apparatus for producing the nanofiber comprising an angle adjustment unit capable of adjusting an installation angle of the liquid raw material discharge unit to the high-pressure gas flow ejected from the high-pressure gas ejection unit.
According to the present invention, there is provided an apparatus for producing the nanofiber wherein at least two or more liquid raw material discharge unit are symmetrically provided to the high-pressure gas ejection unit.
According to the present invention, there is provided an apparatus for producing the nanofiber wherein the liquid raw material discharge units are equally provided around the high-pressure gas flow ejected from the high-pressure gas ejection unit.
According to the present invention, there is provided an apparatus for producing the nanofiber wherein the high-pressure gas flow ejected from the high-pressure gas ejection unit is provided in a vertical direction to an installation surface of the nanofiber producing apparatus.
According to the present invention, there is provided a method for producing a nanofiber by discharging a liquid raw material from a liquid raw material discharge unit to a high-pressure gas flow ejected from a high-pressure gas ejection means, wherein a discharge angle of the liquid raw material discharged from the liquid raw material discharge unit to the high-pressure gas flow is adjusted, when a plurality of the liquid raw material discharge units provided around the high-pressure gas flow ejected from the high-pressure gas ejection unit discharge the liquid raw material.
According to the present invention, there is provided a method for producing a nanofiber using a nanofiber producing apparatus comprising a heating cylinder to which a raw material is fed, a heating unit for heating the heating cylinder, and an extruding unit for extruding the raw material in the heating cylinder, wherein, an end portion of the heating cylinder is provided with a gas ejection hole for ejecting a high-pressure gas, a plurality of raw material discharge units for discharging the raw material in melting state in the heating cylinder are provided around the gas ejection holes, the raw material fed in the heating cylinder is melted or melting state of the same is maintained by heating the heating cylinder by the heating unit, the raw material is discharged from the raw material discharge unit by using the extruding unit, an air current is generated by the gas ejected from the gas ejection hole, and a fiber having nanometer-order diameter is obtained by elongating the discharged raw material along with the air current of the ejected gas from the periphery.
According to the present invention, a nanofiber having a smaller diameter and good quality can be safely produced. Furthermore, when the nanofiber is produced, it is not necessary to apply an apparatus using high voltage, and a problem of an amount of production per unit time which is disadvantage for the meld blown method can be solved by providing a plurality of resin discharge unit.
Hereinafter, the preferred embodiment of the present invention will be described in detail. The present invention is, needless to say, easily applicable to a structure other than the description of embodiments of the present invention within a scope not inconsistent with an object of the invention.
According to the present invention, a nanofiber is formed by supplying a liquid raw material to fluid (preferably, gaseous fluid) ejected in high pressure. In the description, a term “GAS” without specifying composition means gases consisting of any composition and molecular structure. Additionally, in the description, a term “raw material” means all of materials applicable for forming the nanofiber. In the embodiments hereinafter, an explanation will be made for an example using synthetic resin as the “raw material”, but not limited thereto, various kinds of composition material will be usable. The term “liquid raw material” in the description does not limit property of the material to liquid, and includes “molten raw material” applicable for the embodiment 1 forming the nanofiber by melting and extruding a solid raw material from an extruding unit. Moreover, the term “liquid raw material” in the description also includes “dissolved raw material” applicable for the embodiment 2 which forms the nanofiber by dissolving in advance a solid or a liquid raw material in a predetermined solvent so that a predetermined concentration can be obtained, and by feeding by using an appropriate means and discharging or extruding from a discharge holes. The “liquid raw material” of the present invention needs property having viscosity enough to supply (eject, discharge) “raw material” from supplying holes (ejection holes, discharge holes), and “raw material” having such liquid property is described as “liquid raw material” in the present invention.
While detail description will be made hereafter, basic concept of the present invention is common to an apparatus and method for producing the nanofiber explained as the embodiments 1 and 2 of the present invention, and, as shown in
In
Herein, the discharge unit 73a for discharging the liquid raw material is provided at the supply angle θ to the central line 91 of the high-pressure gas flow 90. The raw material supply tangent angle θ is obtained from the following Equation (1)
tan θ=d/(b−a) (1).
The raw material supply tangent angle θ is adjustable within a scope of 0°<θ<90°. As an example, when the “distance a” is equal to 30 mm, the “distance c” is equal to 2 mm, the “distance d” is equal to 7 mm, and pressure of the ejected high-pressure gas is equal to about 0.15 MPa, θ is preferably equal to 200 plus/minus 100.
The raw material supply tangent angle θ should be determined by the “distance a”, the “distance b”, and the “distance d” between the gas ejection holes, and moreover, should be determined by relationship among the opening diameter “distance c” of the high-pressure gas ejection hole, pressure and temperature of the ejected high-pressure gas.
According to the apparatus and method for producing the nanofiber of the embodiment 1 of the present invention, a pellet-shaped raw material (resin) fed into a hopper is supplied and melted in a heating cylinder heated by a heater, and sent to a front part of the heating cylinder by a screw rotated by a motor. The heating cylinder is provided with a head portion, and the high-pressure gas is ejected from the gas ejection hole provided at a center of the head portion. The liquid molten raw material (molten resin) sent to an end of the heating cylinder is supplied (discharged) from the supply unit (the discharge unit) of the liquid molten raw material (molten resin) having a plurality of superfine tubes provided in a downstream side of the gas ejection unit, through inside of the head portion. A plurality of superfine tubes of the discharge units of the liquid molten raw material are provided equally around the gas ejection hole provided at a center. Thereby, the molten resin discharged from the discharge units of the liquid molten raw material is elongated and the fiber having the nanometer-order fiber can be obtained.
According to the apparatus and method for producing the nanofiber of the embodiment 2 of the present invention, configuration is made to eject the high-pressure gas from the gas ejection hole provided at a center thereof, and the liquid dissolved raw material is discharged from a plurality of superfine tubes of the discharge units of the liquid dissolved raw material provided in a downstream side of the discharge units of the liquid dissolved raw material.
Hereinafter, entire structure of a nanofiber producing apparatus according to the embodiment 1 of the present invention will be described in detail referring to
A nanofiber producing apparatus 1 as shown in
A plurality of heaters 4 provided at an outer circumference of the heating cylinder 3 is capable of controlling temperature separately or collectively by a control unit (not shown). According to the present embodiment, four heaters 4 are provided as shown in
The head portion 7 of the present embodiment, as shown in
The head portion 7 shown in
According to this resin discharge unit holding ring 78, if a plurality of the resin discharge units 73 are provided around the gas ejection hole 71 (the opening nozzle), there is achieved greatly increasing productivity of the nanofiber having a uniform diameter and fiber length by arranging a plurality of resin discharge unit 73 at an equal interval, an equal distance (“distance a” from the gas ejection hole), or an equal angle (discharge angle θ).
Referring to
Regarding an arrangement condition of a plurality of resin discharge units 73, it is also capable of forming a nanofiber having an ununiformed diameter or fiber length by changing the number of the resin discharge units 73, an arrangement interval, an arrangement distance (“distance a” from the gas ejection hole), and an arrangement angle θ. According to use of the produced nanofiber, the arrangement condition of the resin discharge unit 73 such as the arrangement interval or the like may be appropriately selected and changed.
In order to adjust the arrangement condition of the resin discharge unit 73 to the gas flow passage 72, a holding adjusting unit 74 for the resin discharge unit 73 is provided. A diameter of the resin discharge hole of the resin discharge needle 73a in the resin discharge unit 73 is very small and the resin discharge needle 73a is susceptible to the effects of stress such as vibrations of an apparatus and pressure of the resin, and therefore, the arrangement condition of the previously mentioned resin discharge unit 73 may be changed and detachment may be occurred from the head portion 7. It becomes necessary to avoid stress on the resin discharge needle 73a if an angle of the resin discharge needle 73a is adjusted and changed, and to make a structure not to detach the resin discharge needle 73a from the head portion 7.
This structure is useful as the adjusting unit of the discharge angle of the molten resin against the ejection has flow, and the resin discharge needle 73a has a shape of very thin pipe. When the nanofiber producing apparatus 1 is operated, big vibration of the pipe may be occurred on the top thereof by driving the motor 6 and the screw 5, and the holding adjusting unit 74 can suppress the vibration effectively. In
Regarding the gas ejection hole 71 and the resin discharge unit 73, as shown in the drawings, the gas ejection hole 71 is provided in a downstream side from the resin discharge unit 73. According to this structure, the molten resin is gradually elongated along with a distribution of ejected gas flow ejected from the gas ejection hole 71, and a fiber having nanometer-order is obtained. By using the heating unit not shown in the drawings, gas is ejected from the gas piping unit 8 as a hot air. Accordingly, the resin discharged from the resin discharge unit 73 has a nanofiber larger in length and smaller in fiber diameter in comparison with the case the normal temperature gas is ejected.
Description will be made of a series of operation of the nanofiber producing apparatus 1 having the above structure. the raw material (the resin) fed into the hopper 2 is melted in the heating cylinder 3 by heating by the heater 4, and sent to a front part of the heating cylinder 3 by a screw rotated by the motor 6. The molten resin arrived at the end of the heating cylinder 3 is discharged from the raw material discharge holes of six resin discharge needles 73 through six resin flow passages 75 provided in the inside of the head portion 7. The discharged molten resin is carried along with an air current generated by the high-pressure and high-temperature gas supplied from the gas piping unit 8 and ejected from the gas ejection hole 71. The nanofiber is formed by elongating the molten resin by the difference in velocity between rapid air current of the high-temperature gas and slow air retained therearound.
According to the embodiment 1 of the present invention, detailed description of the nanofiber producing apparatus was made in which the granular synthetic resin having a fine particle is melted and used as a raw material. As mentioned before, the liquid raw material of the nanofiber is not limited thereto, and a dissolved raw material may be used, which is prepared by dissolving the solid or liquid raw material in the predetermined solvent in advance so as to obtain the predetermined concentration. This is also called as the liquid raw material.
According to the embodiment 2 of the present invention, a solvent storage unit 5A is used having function for extruding the dissolved raw material with the predetermined pressure instead of using the hopper 2, the screw 5 and the motor 6 of the embodiment 1. The gravity caused by difference in height may be applied as the predetermined pressure. The head portion 7A is connected to a solvent supplying hose 3A and the gas piping unit 8. The unit for ejecting gas (illustration omitted) may be provided in the gas piping unit 8 or be introduced from the high-pressure gas supply unit (not shown) to the gas piping unit 8. As shown in
The nanofiber producing apparatus according to the embodiment 2 is, as shown in
In comparison with the structure of the embodiment 1, according to the present embodiment, the dissolved raw material is used which the raw material is dissolved in the solvent, and the nanofiber producing apparatus can be composed without using a complicated component, such as the heating cylinder, the motor, the screw and so on. Thereby, the apparatus becomes small in size and space can be saved. Additionally, since the apparatus becomes small in size, a portable nanofiber producing apparatus can be obtained. In such a portable apparatus, the nanofiber can be formed by spraying the nanofiber to an area where the nanofiber should be attached, and use of a fiber can be expanded.
Though description was made of the embodiments of the present invention in detail, the present invention is not limited to the prescribed embodiments, and various modifications may be possible within a scope of the present invention. For example, in the above embodiment, the horizontal nanofiber producing apparatus is described which the molten resin and the gas ejection hole are provided in a horizontal direction, however it is not limited thereto, there is no problem to arrange the vertical apparatus and method for producing the nanofiber in the downward. If we adopt the vertical apparatus and method, an effect of gravity can be effectively prevented. The extruding unit is explained as the screw 5, however as a die cast method, there is no problem if the solvent is supplied in order and intermittent extrusion is made by using a piston, although countermeasures should betaken against interruption of produced nanofiber. Furthermore, the gas ejection hole 71 may be nozzle shape by forming in a taper shape so as to increase the pressure thereof. Two examples are raised and described about the structure of adjusting the angles of the resin discharge needle 73a, however, there can be applied the structure capable of adjusting the angles of the bellows-type resin discharge unit and so on.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-065171 | Mar 2015 | JP | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15561702 | Sep 2017 | US |
| Child | 17070733 | US |
