JP6187925B2 - Melt electrospinning method - Google Patents

Description

  The present invention relates to a novel melt electrospinning system.

  Nanofiber structures containing nanofibers are used in various fields such as clothing, electricity, automobiles, medical care, and building materials. In recent years, due to diversification of uses of fibers and fiber structures, the fiber diameter is smaller. There is a need for nanofibers.

  In particular, a nanofiber structure using nanofibers with a small fiber diameter has features such as a large surface area, a high space ratio, a small pore diameter, a high air permeability, and a high fluid permeation rate. Therefore, development in special fields such as filter field, clothing field, medical material field, biotechnology field, automobile field and building material field has been actively conducted.

  As a method for producing a nanofiber structure including nanofibers, a melt blown method and an electrospinning (ESD) method are mainly used.

  An example of the Melt Brown method is shown in FIG. 8, as shown in FIG. 8, a thermoplastic resin discharge nozzle 12 provided with a gas blowing nozzle 11, and a collecting unit (see FIG. 8) installed so as to face the thermoplastic resin discharge nozzle 12. (Not shown). The thermoplastic resin discharge nozzle 12 has a substantially cylindrical shape on the proximal end side, a substantially conical shape on the distal end side, extends from the proximal end side to the distal end side along the central axis, and the base of the thermoplastic resin discharge nozzle 12 A tapered conical hole whose diameter is reduced from the end side to the tip side is formed, and the gas blowing nozzle 11 is fitted on the outer periphery of the thermoplastic resin discharge nozzle 12. Further, a high-temperature and high-pressure gas flow path 13 is formed between the outer peripheral surface of the thermoplastic resin discharge nozzle 12 and the inner peripheral surface of the gas blowing nozzle 11.

And the manufacture is performed as follows.
First, the thermoplastic resin is fed from 26 in a state of being heated and melted, and protrudes from the tip through the thermoplastic resin discharge nozzle 12. At the same time, high-temperature gas is blown from the gas blowing nozzle 11 to generate an air flow substantially parallel to the discharge direction of the polymer discharged from the tip of the discharge nozzle 12.

  As a result, the high-temperature gas is collided and compressed and ejected downward through the tip of the discharge nozzle 12 having a low atmospheric pressure. The molten polymer discharged from the tip of the discharge nozzle 12 is stretched by this high-temperature gas flow to form fibers. The fibers are gradually deposited on the collection part by the suction device to form a fiber structure.

  However, since the Melt Brown method is shaped so that hot air is collided and compressed at the tip of the discharge nozzle 12 from the left and right, mechanical compression / expansion vibration occurs and the fibers become short fibers. Further, when the speed of the high-temperature gas is increased, the period of mechanical vibration becomes faster, and finally the molten polymer is crushed into fine particles and cannot be fiberized. For this reason, the speed of the high-temperature gas cannot be increased. Since the high-temperature gas cannot be increased in speed, it is difficult to make nanofibers of 1 mμ or less in the Melt Brown method, and there is a problem that fibers per nozzle cannot be mass-produced.

  Furthermore, the reason why nanofibers cannot be produced by the Melt Brown method is that the speed of the high-speed gas cannot be increased because the air discharge part is largely open.

  Next, as an example of the ESD (electrospinning) method, as shown in FIG. 9, a discharge nozzle 21 filled with a polymer diluted with a solvent and a tip 22 of the discharge nozzle 21 are disposed so as to face each other and are rotatable. A high-voltage power source 24 that applies a high voltage between the tip 22 and the collector 23, and a syringe pump (not shown) that discharges a polymer diluted with a solvent at a constant flow rate from the tip of the discharge nozzle 21. A).

And the manufacture is performed as follows.
First, the blowing nozzle 21 is filled with a polymer solution swollen with a solvent, and a high voltage is applied between the tip 22 and the collector 23 by a high voltage power source 24. At the same time, the syringe pump is operated to discharge the polymer solution swollen with the solvent from the tip 22 syringe at a constant speed. The tip is deformed into a conical shape and pushed out. Since the polymer solution swollen with the extruded solvent is charged to the same polarity, it is stretched by electrostatic repulsion. The solvent evaporates from the polymer solution swollen with the stretched solvent, the charge density is increased, and further stretching is performed to form ultrafine fibers. The charged fiber is attached to a collecting portion charged to a different polarity. And it accumulates on this fiber collection part 23, and a nanofiber structure is formed.

  However, in the ESD method, only a minute amount of nanofiber is produced from the tip of one capillary. For this reason, a method of mass production with a simple configuration in which a large number of capillaries are equipped and electrostatic spraying is performed from a large number of capillaries has been carried out until now, but the method using such a large number of capillaries is an electric field. Maintenance is very difficult because it requires a large spray area to avoid interference. In addition, when a flammable organic solvent and a high voltage are used, an explosion is likely to occur. As a result, the advantage that the solvent can be produced at normal temperature and normal pressure, which is an advantage of the ESD method, has been impaired by producing only a polymer that uses water or a solvent that does not ignite or does not easily ignite. Because of these problems, the manufacturing cost of nanofibers has become very high.

  In addition, regarding the problem of the quality of nanofibers produced by the ESD method, when a large amount of nanofibers are produced using the ESD method in a narrow space, the polymer solution does not become a fiber, and droplets or ball-shaped substances are the basis. Stick on top. In addition, since the droplets and the ball-shaped substance cause the material utilization efficiency to be significantly reduced and the resulting nanofiber layer is clogged, the mechanical properties of the nanofiber layer may be greatly impaired. For example, when used as a filter medium, there has been a problem that the performance of the filter is degraded.

  Accordingly, the present invention is intended to solve these problems, and a first object of the present invention is to provide a melt electrospinning method (hereinafter referred to as a Melt ESD method).

  The second object of the present invention is to form a nanofiber structure by the Melt ESD method.

  The third object of the present invention is to enable mass production of optimal nanofibers without generating droplets or beads.

  The fourth object of the present invention is to prevent the phenomenon of electric field interference and ionic wind and form a nanofiber structure having a uniform layer thickness.

  The fifth object of the present invention is to enable long-time spraying by suppressing the Coulomb force and preventing the nanofibers from adhering to the nozzles and electrode balls.

  The sixth object of the present invention is to eliminate the risk of explosion, electric shock and exposure.

  The seventh object of the present invention is to form a nanofiber structure characterized by having the function of a heat insulating material by the Melt ESD method.

  An eighth object of the present invention is to form a nanofiber structure characterized by having a function of a sound absorbing material by the Melt ESD method.

  The ninth object of the present invention is to form a contaminated water treatment filter capable of efficiently removing oil and fine substances (plant, dust, fungi, virus) and the like by the Melt ESD method.

  The tenth object of the present invention is to form a nanofiber structure for removing radioactive substances such as iodine 131, cesium 134, cesium 137, etc. by Melt ESD method.

  An eleventh object of the present invention is to provide a nanofiber structure at a low cost.

The first solution of the present invention is to provide a Melt ESD method in which heat is applied to a thermoplastic polymer to swell and nanofibers are generated using high-speed and high-temperature air and electric charge.
In other words, the melt ESD method is a melting method nanofiber manufacturing method that shares wind and electric charge.

  The second solution of the present invention is that the Melt ESD system is a mechanism that melts a thermoplastic polymer, a nozzle that discharges the molten polymer, an air that generates high-speed and high-temperature air that is used to stretch the molten polymer discharged from the nozzle. It consists of a nozzle, an electrode that generates electric charge at the tip of the nozzle that discharges molten polymer, and an insulating plate that blocks electric field interference to the nozzle due to electrostatic induction from charged nanofibers. The nozzle is covered with a heat insulating material that also serves as

  According to the third solution of the present invention, when the melt ESD method is used, the different thermoplastic polymers or the single thermoplastic polymers are mixed in the pellet state or used alone to form nanofibers, thereby forming each of the different thermoplastic polymers. It is to create a heat insulating material composed of a nanofiber structure having the characteristics of each polymer without impairing the polymer characteristics.

  The fourth solution of the present invention is that when using the Melt ESD method, different thermoplastic polymers or single thermoplastic polymers are mixed or used alone in a pellet state and nanofibrinated to form each of the different thermoplastic polymers. It is to create a sound-absorbing material composed of a nanofiber structure having the characteristics of each polymer without impairing the polymer characteristics.

  The fifth solution of the present invention is that, when using the Melt ESD method, the different thermoplastic polymers are mixed in a pellet state and made into nanofibers so that the respective polymer properties of the different thermoplastic polymers are not impaired. It is to create a filter for treating contaminated water that can efficiently remove oils and fine substances (plants, dust, fungi, viruses) composed of nanofiber structures that have both properties.

  The sixth solution of the present invention is to create a decontamination filter capable of removing cesium as a radioactive material by mixing brussian blue into a different thermoplastic polymer and impregnating nanofibers when using the Melt ESD method. It is.

  Examples of the thermoplastic polymer that is a material of the nanofiber used in the melt ESD method include polyester, polyamide, polyolefin, and polyurethane (PU). Examples of the polyester include polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), and polylactic acid (PLA). Examples of polyamide include nylon 6 (N6), nylon 66 (N66), nylon 11 (N11), and the like. Examples of the polyolefin include polyethylene (PE), polypropylene (PP), and polystyrene (PS).

As described above, the nanofiber structure manufactured by the Melt ESD method of the present invention has the following effects.
(1) By connecting the nozzle side to GND, the power supply of the high-voltage power supply is made zero, so that positive charges can be supplied from GND, so mass production is possible without generating droplets or beads due to leakage. What made it possible.
(2) Since the high voltage power supply only causes electrostatic induction, no current is required and the number of nozzles can be connected indefinitely.
(3) Without using an organic solvent, heat was applied to the thermoplastic polymer to make it swell, and nanofibers were generated using high-speed air and electric charge, so there was no danger of explosion because no solvent was used. There is no danger of exposure to workers.
(4) The formation of a nanofiber layer having a uniform layer pressure while preventing electric field interference and ion wind phenomena.
(5) A reduction in the amount of charge at the nozzle tip is prevented, enabling long-time spraying.
(6) Since the polymer solution side is GND, electrical leakage is eliminated. In addition, this electrical leakage has enabled the safety of workers.
(7) Since it is not necessary to insulate the polymer solution supply related device, the device has a very safe and simple configuration.
(8) Since electric lines of force can be concentrated at the tip of the nozzle, a large amount of nanofibers can be created from one nozzle, and it is not necessary to equip a large number of nozzles.
(9) Since mass production is possible with a simple configuration, production cost can be reduced, and power consumption and maintenance cost are not required, and there is a great effect in terms of cost.
(10) Since it is a simple device, it is easy to handle and has the effect of requiring less trouble for maintenance.
(11) Since the production and collection of nanofibers can be separated, the amount of nanofibers produced can be increased freely, and the collection part can be adapted according to the product.
(12) nanofiber structures produced by Melt ESD scheme of the present invention is to have insulation, the function of the intake sound material.
(13) Oil and water can be separated from contaminated water containing oil, and the oil can be completely recovered.
(14) Seawater containing salt can be discharged as it is. Separation and collection of minute waste with radioactive material attached.
(15) Cesium can be recovered.
(16) The amount of radioactive waste is extremely small.

The basic composition figure of a Melt ESD system. The figure which shows the flow of the high-speed air of a Melt ESD system. The figure which shows the flow of the high-speed air of a conventional system. The figure which shows the flow of the high-speed air at the time of using a rubber nozzle. The figure which shows the collection system of a charged nanofiber. The figure which shows a mobile sewage treatment apparatus. The figure which shows a mobile pollution soil washing | cleaning apparatus. The figure which shows an example of a Melt Brown system. The figure which shows an example of an ESD system.

  Hereinafter, a nanofiber structure manufactured by the Melt ESD method and the Melt ESD method of the present invention will be described with reference to the accompanying drawings.

  The Melt ESD method will be described.

  1 is a mechanism for melting a thermoplastic polymer, 2 is a nozzle for discharging the molten polymer, 3 is an air nozzle for generating high-speed air used to stretch the molten polymer discharged from the nozzle, and 4 is for discharging molten polymer An electrode 5 for generating electric charge at the tip of the nozzle 2 is an insulating plate for blocking electric field interference due to electrostatic induction from the charged nanofibers. Furthermore, the nozzle 2 is covered with a heat insulating material 6 that prevents heat dissipation and also serves as insulation.

  In the nanofiber generation process, first, the thermoplastic polymer clay is heated and melted by the mechanism 1 for melting the thermoplastic polymer until the clay of the thermoplastic polymer is sufficiently lowered. Next, the molten polymer is discharged from the nozzle 2 and at the same time, high-temperature high-speed air is ejected from the air nozzle 3 to stretch the molten polymer. At the same time, a high voltage is applied between the electrode 4 and the nozzle 2 to generate a charge, and the molten polymer is charged to the same polarity. The homopolar charges repel each other by Coulomb force, thereby further stretching the molten polymer. This produces nanofibers.

  At this time, high-speed high-temperature air is dominant in the force for stretching the molten polymer. The high-speed and high-temperature air forms a gentle pressure difference flow around the high-speed and high-temperature air by entraining surrounding air. By placing the nozzle at the position shown in FIG. 2, the molten polymer is drawn in by the high-speed and high-temperature air and travels on the high-speed high-temperature air in the center while riding on the air with a moderate air pressure difference. It is stretched with air at high speed to be fiberized. Since nanofibers are produced in this way, mass production is possible with a simple configuration.

  At this time, what is important is that the high-speed high-temperature air must be separated from the tip of the nozzle 2 for discharging the molten polymer. That is, in order for the molten polymer to be stretched, gentle air in which high-speed and high-temperature air is involved is necessary. When the nozzle is brought close to high-speed and high-temperature air, as shown in FIG. 3, the pressure difference is large and a smooth stretching operation is not performed, and the molten polymer becomes fine particles.

Here, what is important in the positional relationship between the high-speed and high-temperature air and the nozzle is a smooth stretching operation by separating the distance, but if it is separated too much,
1. The power to wind up with high-speed air is lost.
2. The temperature of the molten polymer decreases and the viscosity increases.
There are problems such as. In addition, the molten polymer is rapidly cooled by releasing high-speed and high-temperature air and solidification heat during the stretching operation. For this reason, a heater 7 is used in front of the air nozzle 8 as shown in FIG. As a result, 1. By rapidly heating the compressed air and causing thermal expansion, the high-speed and high-temperature air generated by the compressed air can be further accelerated.
2. It is possible to delay the cooling of the molten polymer by heating to a temperature higher than that of the molten polymer by the high-speed high-temperature air heated by the heater 7.
3. The molten polymer discharged from the nozzle 2 can be heated again while it reaches the high-speed and high-temperature air.
Etc. can be improved.
Further, when the polymer falls below a certain viscosity, the relationship between the wind speed v (m / s), the discharge amount U (g), and the fiber diameter φ (nm) is established as follows.
If the specific gravity of the polymer is k
U = kφ · v
It was verified by experiments that the fiber diameter became 100 to 200 nm by reducing the discharge amount and increasing the wind speed. That is, when producing a finer nanofiber, the nanofiber can be produced by increasing the wind speed or decreasing the discharge rate. From these experiments, it was found that nanofibers can be produced without reducing the nanofiber production by using air with increased air velocity. Therefore, as shown in FIG. 4, stable nanofibers can be generated by using the rubber nozzle 8 to generate ultrasonic wind and use high-speed and high-temperature air.

  Next, as shown in FIG. 5, when the charged nanofibers are collected from the nozzle 2 to which a high voltage is applied to the molten polymer melted by the mechanism 1 for melting the thermoplastic polymer, the molten polymer is charged. The Thereby, the repulsive force (Coulomb force) due to the homopolar charge of the charged polymer solution is combined with the drawing force of the high-speed and high-temperature air to further reduce the thickness. At this time, the charged charged fibers cause the charged nanofibers to be attracted toward the collecting drum (reverse electrode) 9 by causing the electrode 4 to generate a charge different from that of the charged nanofibers on the collecting drum 9. To form a thin layer of nanofibers. The nanofiber thus formed is formed as a nanofiber structure and is used as a heat insulating material or a sound absorbing material.

A nanofiber structure in which a contaminated water treatment filter is formed by the Melt ESD method using a water repellent material and a hydrophilic material or different polymers having different melting points will be described.

When the transfer polymer is mixed in the pellet state by the Melt ESD method, the different polymers do not mix with each other, and thus become nanofibers in an independent state. As a result, the different polymer is dispersed in the nanofiber state. As a result, the polymer has the characteristics of each polymer.
Specifically, Example 1: In the case of polypropylene (90%) + polylactic acid (10%) Polypropylene is water -repellent and becomes super-water-repellent when it is made into nanofibers and does not allow water to pass through at all. Polypropylene, on the other hand, is lipophilic and has a large surface area that absorbs large amounts of oil. Since the polylactic acid nanofibers are hydrophilic, they adsorb water. Therefore, a water filter using nanofibers in which polypropylene and polylactic acid are dispersed can remove oil and contaminants and allow water to pass through when passing sewage containing oil.
Example 2: Polypropylene (80%) + polyester (20%) The melting point of polypropylene is 180 degrees and the melting point of polyester is 240 degrees. By mixing these and melting at an appropriate temperature, nanofibers having greatly different fiber diameters can be dispersed. This makes it possible to create a material with resilience.
Example 3: Polypropylene (90%) + Polyurethane (10%) When the resulting nanofibers are heated, the low melting point polyurethane melts and bonds the polypropylene fibers. This makes it possible to create a strong polypropylene sheet.

  A nanofiber structure in which a decontamination filter is formed by the Melt ESD method will be described as a method for removing radioactive substances from contaminated water.

  On March 11, 2011, radioactive materials were released due to a radioactive material leakage accident at the Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Station following the Great East Japan Earthquake. These radioactive substances are mainly iodine 131, cesium 134, and cesium 137. In this case, since the half-life of iodine 131 is 8 days, there is no problem, but cesium 137 has a problem that the half-life is as long as 30 years. Cesium is volatile and has a property of being well dissolved in water. Therefore, cesium also scatters when the water containing cesium evaporates.

  Therefore, the necessary conditions for the nanofiber structure for removing radioactive substances from contaminated water are as follows: (1) cesium can be recovered, (2) less radioactive waste, (3) less expensive, (4) ▼ Able to process in large quantities, ⑤Can recover oil, ⑥Do not absorb salt from seawater.

  As a method of satisfying these conditions, nanofibers of 1 Kg / nozzle per hour can be produced by Melt ESD method using a different polymer of polypropylene and polyester, but polypropylene and polyester are water repellent and nano By using fibers, the surface area is increased, resulting in super water repellency and impervious water. For this reason, alcohol is used while reducing the surface tension of water, but it is expensive to perform the decontamination treatment. Therefore, by making polypropylene and polyester nanofibers and dispersing them with polypropylene and polyester nanofibers, water can be passed without using alcohol. Moreover, when using a recycled product etc., it is 10-20 yen / Kg, and the quantity used at once is 10 g, and it can be used for 100 times with this amount.

  Furthermore, in order to adsorb cesium, zeolite and porous beads are carried on polypropylene and polyester nanofibers and collected. Zeolite and porous beads can be supported on polypropylene and polyester when the diameter is 0.1 to 0.05 μm. Nanofibers have a very large surface area and can efficiently remove cesium. When using zeolite or porous beads as they are, if the cesium of zeolite or porous beads adheres and scatters, the lung easily reaches the lungs and the inner coating continues. These cannot be prevented even with N95 and N100 dust masks. However, when nanofibers are impregnated with zeolite or porous beads, they are long fibers (10 cm or more) and are safe without entering the lungs. Furthermore, zeolite and porous beads are also inexpensive and are used in small amounts because they impregnate nanofibers.

  Polypropylene, polyester, polylactic acid, polyvinyl alcohol, zeolite, and porous beads do not adsorb salt from seawater. For this reason, salt can be passed through, for example, when 87,500 tons of contaminated water including seawater used for cooling at the beginning of the accident at the Fukushima nuclear power plant is treated.

The nanofiber structure having the function of the contaminated water treatment filter can efficiently remove oil and fine substances (plankton, dust, fungi, viruses) and the like while being small. Therefore, the following functions are exhibited while moving by installing in a mobile sewage treatment apparatus as shown in FIG.
1. There is no need to construct a sewage treatment plant (plant), and treatment of contaminated water can be started in a short period of time.
2. By adjusting the number of containers, the sewage treatment capacity can be changed according to the amount of sewage.
3. It can pinpoint dirty places on rivers and coasts.
4). Since the mobile sewage treatment apparatus can be mass-produced at a factory, the sewage treatment apparatus can be produced at low cost.
5. There is no need for foundation work, and after sewage treatment, it can be restored to its original state without damaging the natural beauty.

  Furthermore, the nanofiber structure having the function of the decontamination filter can efficiently remove radioactive substances such as cesium while being small. Therefore, the following functions are exhibited while moving by installing the mobile contaminated soil cleaning apparatus as shown in FIG.

Cesium is highly volatile and dissolves well in water. Therefore, cesium can be dissolved in water by washing with water. Cesium can be recovered by passing the water containing cesium through a decontamination filter. Therefore, the mobile contaminated soil cleaning apparatus has a function of cleaning soil and rubble contaminated with radioactive substances. This feature is Cessium can be removed by washing soil and debris contaminated on site with water.
2. Since water is recycled and reused, it can be processed with a minimum amount.

  Note that the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage, and a plurality of components disclosed in the embodiments. Various modifications can be made by an appropriate combination of the above.

  As a method for producing a nanofiber structure containing nanofibers, a MeltBlown method and an ESD method have been mainly used. However, each is not fully satisfactory, and an improved method for producing a nanofiber structure has been desired. Therefore, after various researches, we developed the Melt ESD method, which combines only the advantages of the conventional Melt Brown method and ESD method, and developed a nanofiber structure that has the functions of a heat insulating material, a sound absorbing material, an oil / water separation filter, and a decontamination filter. As formed, the present invention is extremely useful in industry.

DESCRIPTION OF SYMBOLS 1 ... Mechanism to melt thermoplastic polymer 2 ... Nozzle 3 ... Air nozzle 4 ... Electrode 5 ... Insulating plate 6 ... Insulating material 7 ... Heater 8 ... Rubber nozzle DESCRIPTION OF SYMBOLS 11 ... Gas blowing nozzle 12 ... Discharge nozzle 13 ... Heating gas flow path 14 ... Heater 21 ... Discharge nozzle 22 ... Tip 23 ... Collection drum 24 ... High voltage Power supply

Claims (1)

Mechanism for melting thermoplastic polymer, nozzle for discharging molten polymer, air nozzle for generating high-speed high-temperature air used to stretch the molten polymer protruding from the nozzle, and tip of the nozzle for discharging molten polymer And an insulating plate for blocking electric field interference to the nozzle due to electrostatic induction from charged nanofibers. The nozzle is covered with a heat insulating material and has a mechanism for melting the nozzle and the thermoplastic polymer. The structure is such that the air nozzle, nozzle and electrode are arranged in a straight line, and the nozzle is placed at a position offset from the flow of high-speed high-temperature air ejected from the air nozzle. Added to make it swollen and to generate nanofibers using high-speed, high-temperature air and electric charge. Electrospinning method.

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