JP4876252B2 - Method for producing extra fine fibers - Google Patents

Description

  The present invention relates to an ultrafine fiber having a very small diameter and high uniformity in diameter and excellent physical properties without using a solvent, and a method for producing the same.

  The method of manufacturing a nonwoven fabric consistently and continuously by making a thermoplastic raw material fiber by melt spinning, blowing the fiber with a high-speed gas and collecting it in a sheet form on a collecting plate is called a melt blown method, For example, it is disclosed in Patent Document 1. In addition, for example, the electrospinning method disclosed in Patent Document 2 is a method in which a solution spinning method is used for fiberizing and a nonwoven fabric is continuously manufactured.

Japanese Patent Laid-Open No. 49-10258 Japanese Patent Laying-Open No. 2005-330624

  However, it is considered difficult to mass-produce fibers having a diameter of about 3 μm or less by a direct spinning method such as a melt blown method. Further, since the melted raw material resin is extruded from a thin nozzle, the molecular weight of the raw material resin is limited, and improvement in physical properties cannot be expected. Diameter unevenness tends to increase. Solution spinning methods such as the electrospinning method are not preferable from the viewpoint of the burden on the global environment because they require a cost for recovering the solvent and it is extremely difficult to recover the solvent completely.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an ultrafine fiber having a high uniformity of diameter and excellent physical properties without using a solvent. And

The ultrafine fiber manufacturing method of the invention according to claim 1, which has been made to achieve the above object, irradiates the thermoplastic polymer melt discharged from the nozzle with infrared rays, and the thermoplastic polymer melt. with the temperature a high voltage is applied between the thermoplastic polymer crystalline melting temperature or the thermoplastic polymer melt and the target was sufficiently low viscosity to 50~500K allowed to warm to a temperature higher than the softening temperature of the , to accelerate the thermoplastic polymer melt was low viscosity by applying an air flow, which narrowed the thermoplastic polymer melt below 5μm playing to the target by an electric field attraction of high voltage It is characterized by that.

Similarly, the ultrafine fiber manufacturing method of the invention according to claim 2 is the method of manufacturing the ultrafine fiber according to claim 1, wherein the temperature of the thermoplastic polymer melt is set to the crystal melting temperature or softening temperature of the thermoplastic polymer. The temperature is raised to a temperature 100 to 300K higher than that .

The ultrafine fiber manufacturing method of the invention according to claim 3 is the method of manufacturing the ultrafine fiber of claim 1, wherein the nozzle is an extruder nozzle .

The ultrafine fiber manufacturing method of the invention according to claim 4 is the method of manufacturing the ultrafine fiber of claim 1 , wherein the distance between the nozzle and the target is 2 to 300 mm .

According to a fifth aspect of the present invention, there is provided a method for producing the ultrafine fiber according to the first aspect, wherein the infrared ray is a laser beam .

The ultrafine fiber manufacturing method of the invention according to claim 6 is the method of manufacturing the ultrafine fiber of claim 5 , wherein the laser beam is a carbon dioxide laser.

The ultrafine fiber manufacturing method of the invention according to claim 7 is a method of manufacturing the ultrafine fiber according to claim 1, wherein the end portion of the nozzle is inserted into the cylindrical space portion at one end and in the vicinity of the other end. A melt blow die having an air inlet and a laser beam irradiation port and an electrode sequentially provided below the nozzle is used to apply the laser beam to the thermoplastic polymer melt discharged from the nozzle. Irradiation is performed, and an electric field is formed by applying a direct current between the electrode and the nozzle while flowing an air flow from the air inlet .

  The temperature rise due to laser irradiation is preferably 50 to 500 K higher than the crystal melting temperature or softening temperature of the thermoplastic polymer, and is 100 to higher than the crystal melting temperature or softening temperature of the thermoplastic polymer. A temperature higher by 300K is more preferable. By setting the temperature to such a level, the thermoplastic polymer can have a sufficiently low viscosity, and can be stretched and thinned by the attractive force of the electric field. At temperatures lower than this, the thermoplastic polymer cannot be sufficiently reduced in viscosity to be stretched by an electric field, and ultrafine fibers cannot be obtained by this method. When the temperature is higher than this temperature, decomposition proceeds before the fibers are stretched by an electric field and cooled and solidified, so that excellent ultrafine fibers cannot be produced.

  Therefore, in order to produce a good ultrafine fiber, it is necessary to raise the temperature to an appropriate temperature. For this purpose, it is preferable to actually measure and control the maximum temperature reached by the thermoplastic polymer after laser irradiation, but in fact, the temperature is instantaneously raised and stretched by an electric field, and cooled and solidified. It is generally difficult to measure and control directly with high accuracy. However, since the maximum temperature can often be measured without applying an electric field, it is preferable to actually measure in this case. On the other hand, when the decomposition of the sample proceeds or the sample size is small, the temperature accuracy cannot be ensured by direct measurement. In this case, since the temperature accuracy obtained by calculation is higher, it is more reasonable to adopt this.

  The maximum temperature reached by the thermoplastic polymer after laser irradiation is the temperature of the thermoplastic polymer before laser irradiation, the output of the laser light source, the irradiation efficiency of the laser beam, the irradiation time, and the heat at which the laser beam is irradiated. From the volume of the plastic polymer and the density and specific heat of the thermoplastic polymer, it can be estimated by the following equation.

Maximum temperature = pre-irradiation temperature + laser output x irradiation efficiency x irradiation time / (specific heat x density x volume)
For example, consider a case where the temperature of a PET having a crystal melting temperature of about 250 ° C., a density of about 1.3 g / cm ³ and a specific heat of 2.3 kJ / kg / K is increased from 20 ° C. to 370 ° C., 120K higher than the crystal melting temperature. It is sufficient to irradiate energy of about 1.0 J per 1 mm ^{3 of the} thermoplastic polymer. Therefore, considering the case of irradiating a 1 mm ³ PET with an output of 10 W laser with an irradiation efficiency of 0.5, the laser irradiation time is about 0.2 seconds. When supplying PET continuously, it is only necessary to supply 1 mm ³ PET in 0.2 seconds, so the sample flow rate is 5 mm ³ / sec, that is, the temperature is raised to the required temperature if PET is supplied at a mass flow rate of about 0.4 g / min. can do. Similarly, to raise the temperature of a PET melt at 280 ° C to 450 ° C, 200K higher than the crystal melting temperature, the laser irradiation time may be about 0.1 second, and the sample flow rate when PET is continuously supplied is 10 mm ³ / Second, that is, a mass flow rate of about 0.8 g / min.

  Here, the irradiation efficiency is a numerical value in the range of 0 to 1 that represents the proportion of energy absorbed by the thermoplastic polymer that becomes the fiber raw material in the irradiation energy of the laser light, and is the value of the irradiated thermoplastic polymer. It depends on the form, the shape of the laser beam, and the optical system for irradiation. A weak laser beam is irradiated onto a sample of known size and properties, and the irradiation efficiency is calculated by measuring the maximum temperature and used for temperature estimation during manufacturing.

The ultrafine fiber manufacturing method of the invention according to claim 8 is a method for manufacturing the ultrafine fiber of claim 1, wherein the high voltage is 1 to 40 kV, and the average electric field of the high voltage is 0.05 to 1. 0.0 kV / mm . When the electric field is more than this, the electric field is not stable because sparks are easily generated between the electrodes. On the other hand, when the electric field is less than this, the thermoplastic polymer having a sufficiently low viscosity cannot be efficiently stretched by the electric field.

  The ultrafine fiber manufacturing method of the invention according to claim 9 is a method of manufacturing the ultrafine fiber of claim 1, wherein the target is a collection plate, and the above-mentioned thinned plate on the collection plate It is characterized in that ultrafine fibers are captured randomly.

  The ultrafine fiber manufacturing method of the invention according to claim 10 is a method of manufacturing the ultrafine fiber of claim 1, wherein the target is a bobbin, and the thinned ultrafine fiber is wound around the bobbin. It is characterized by that.

  An ultrafine fiber manufacturing method according to an eleventh aspect of the invention is a method for manufacturing the ultrafine fiber according to claim 2, wherein the air flow velocity is 0.1 to 500 m / sec, and the air flow temperature is 0 to 600. It is characterized by being at ° C.

  According to the method for producing ultrafine fibers of the present invention, the raw material thermoplastic polymer is irradiated with infrared rays, which are high-energy heat rays, and rapidly made into a melt having a very low viscosity, thereby spinning by spinning with an attractive force of an electric field. Very thin fibers can be made. This method makes it possible to mass-produce ultrafine fibers having a diameter of about 3 μm or less, which has been impossible with a direct spinning method such as a conventional meltblown method, without using a solvent. Since the polymer can be brought into a molten state having a sufficiently low viscosity at the time of spinning, even if the molecular weight of the polymer is large, spinning can be performed without breaking the yarn. In addition, immediately after the temperature is rapidly raised by infrared irradiation and the melt is sufficiently low in viscosity, it is stretched by the attractive force of the electric field and rapidly cooled and solidified, so the time of high temperature and low viscosity is extremely short, due to thermal decomposition. Degradation of physical properties can be avoided. Therefore, fibers excellent in physical properties such as yarn strength can be obtained. Diameter unevenness is also reduced. With this manufacturing method, it is also possible to control the fiber orientation in the resulting fiber assembly by controlling the electrode shape for electric field formation and the potential distribution between the electrodes.

Further, since no solvent is used, it is preferable not only from the viewpoint of not requiring the solvent recovery cost, but also from the viewpoint of environmental maintenance such as resource saving and the absence of solvent scattering.
Furthermore, according to the method for producing ultrafine fibers of the present invention, ultrafine fibers can be produced continuously, and further, a nonwoven fabric can be produced continuously with the ultrafine fibers. Therefore, it is a highly productive manufacturing method, and ultrafine fibers and non-woven fabrics can be manufactured at low cost.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments for carrying out the present invention are as follows.
FIG. 1 is a diagram showing a schematic configuration of an example of an apparatus for carrying out an ultrafine fiber manufacturing method to which the present invention is applied. This is an example of using a fibrous thermoplastic polymer as a raw material. As shown in the figure, the raw fiber 1 is irradiated with a laser beam 11 and melted, and is spun by a high-voltage electric field attractive force to reach a collecting plate 9 that is a target as an ultrafine fiber 10 and is captured.

  The raw fiber 1 is, for example, polyethylene terephthalate, which is polyester, and has a softening point to a melting point of 240 to 250 ° C. A polyester raw fiber 1 having a thickness of 10 to 1000 μm, which is about 10 to 1000 times the diameter of the target ultrafine fiber 10 having a diameter of 0.01 to 5 μm, is wound around a reel 8. The raw fiber 1 is guided in the direction of travel by the deflection roller 3 and pulled by the nip rolls 6a and 6b and the nip rolls 4a and 4b, which are driven by motors (not shown), respectively, and after passing through the orifice (needle) 5. Get out.

  At the outlet of the orifice 5, a carbon dioxide laser 7, which is an infrared source, sets a target and irradiates the raw fiber 1 with the laser beam 11. The irradiation time of the laser beam 11 is not less than 0.1 milliseconds and not more than 1 second. By this irradiation, the temperature of the raw material polymer is heated to a temperature sufficiently higher than the higher one of the melting point of the raw material polymer or the glass transition temperature. . Thereby, the polyester of the raw fiber 1 is softened and melted. On the other hand, a DC high voltage is applied from the power source 12 between the orifice 5 and the collection plate 9. The melted raw material fiber 1 is crushed by the electric field attraction, becomes an ultrafine fiber 10 having a target diameter, and becomes a fiber assembly randomly captured on the collection plate 9.

  If the amount of extra fine fibers captured is further increased from this state and subjected to adhesion treatment or heat fusion treatment, a nonwoven fabric can be obtained. The fiber assembly or nonwoven fabric can be used for filters, battery separators, medical applications, clothing, and the like.

  FIG. 2 is a diagram showing a schematic configuration of an example of an apparatus for carrying out the method for producing ultrafine fibers to which the present invention is applied. An example is shown in which the raw thermoplastic polymer is a molten resin 28 discharged from the nozzle 20 of the extruder 22. As shown in the figure, the molten resin 28 is heated by being irradiated with infrared rays, and melted sufficiently low in viscosity. The melted resin 28 is spread by a high-voltage electric field attraction, and is collected into a bobbin 29 as an ultrafine fiber 10. . At this time, if the rotational speed of the bobbin is sufficiently higher than the yarn speed caused by the electric field, the bobbin is wound up as a single fiber. If the rotation speed of the bobbin is smaller than the yarn speed caused by the electric field, the bobbin is collected in a web state made of ultrafine fibers. The obtained fiber or web is stretched after the bobbin 29, whereby molecular chains and fibers can be arranged to control physical properties.

  The raw material thermoplastic polymer is, for example, nylon (registered trademark) pellets which are polyamide resins. The nylon pellets are melted and extruded by the extruder 22. In the extruder 22, a screw 24 is inserted into a cylinder 27 with a heater, and a hopper 23 is attached. The screw 24 is connected to the motor 25 by a belt. When the nylon pellets are introduced from the hopper 23, they are kneaded by the rotation of the screw 24 while being heated by the cylinder 27, progressing while being softened and melted, and are discharged into the melt state 28 from the nozzle 20.

  In the nozzle 20, the infrared light emitting diode 26 sets a target and irradiates the melted resin 28 with infrared rays. By this irradiation, the temperature of the nylon of the molten resin 28 rises and the viscosity is sufficiently lowered. On the other hand, a high DC voltage is applied from the power supply 12 between the nozzle 20 and the bobbin 29 (distance D = 2 to 300 mm). The molten resin 28 is thinned by the electric field attraction and becomes the ultrafine fiber 10 having a target diameter. The ultrafine fiber 10 is wound around a bobbin 29 connected to a motor (not shown), and is used for various applications as an infinitely long single fiber or fiber web.

  FIG. 3 is a view showing a schematic configuration of an example of an apparatus for carrying out the method for producing ultrafine fibers to which the present invention is applied. In this apparatus, an extruder 22 and a melt blown die 30 are integrated. In the drawing, the melt blown die 30 partially represents a cross-sectional structure. In the extruder 22, a screw 24 is inserted into a cylinder 27 with a heater, and a nozzle 20 and a hopper 23 are attached. The screw 24 is connected to the motor 25 by a belt. A part of the nozzle 20 of the extruder 22 is inserted into the melt blown die 30. The melt blown die 30 is hollow and has a space S and a cylindrical space T. One end of the cylindrical space T is provided with an air inlet 13a. The melt blown die 30 includes air inlets 13b and 13c near the other end of the cylindrical space T. The air inflow portions 13a, 13b, and 13c are independently connected to an external compressor (not shown).

  The melt blown die 30 is provided between the cylindrical space T below the tip of the nozzle 20 and the outside, and on the outside of the space perpendicular to the insertion direction of the nozzle 20. A gas laser 7 is provided, and a laser transmitting material 32 is provided on the cylindrical space T side of the space. Further, the electrode 14 is embedded below the installation portion of the laser transmitting material 32, and a part of the electrode 14 is exposed to the cylindrical space portion T. This electrode 14 is connected to an external power source. The melt blown die 30 is engaged with the conveyor 19, the suction 17 and the bobbin 29. The conveyor 19 is held by nip rolls 18 a and 18 b and nip rolls 18 c and 18 d that are vertically arranged at the left and right ends of the space S of the melt blown die 30, and is supported by the four deflection rollers 3 outside the melt blown die 30. Each nip roll and each deflection roller 3 are connected to a motor (not shown). The bobbin 29 is provided outside and connected to a motor (not shown) so that one end thereof is positioned on an extension line on the upper portion of the conveyor 19. Further, the suction 17 is ventilated with the space S of the melt blown die 30 through the vent pipe 16.

  The ultrafine fiber 10 by the apparatus of FIG. 3 is manufactured as follows. The molten resin 28 is discharged from the extruder 22 into the melt blown die 30, becomes the ultrafine fiber 10 through the cylindrical space portion T and the space portion S in the melt blown die 30, and is guided by the conveyor 19 to the external bobbin 29. It is wound up. More specifically, when a pellet of nylon, which is a raw material thermoplastic polymer, is introduced from the hopper 23, it is heated by the cylinder 27 and is kneaded by the rotation of the screw 24 while being softened and melted. The nozzle 20 is discharged into the melt blown die 30. At this time, the laser beam 11 is emitted from the carbon dioxide laser 7 to the irradiation port 31 through the laser transmitting material 32. The discharged molten resin 28 is irradiated onto the laser beam 11 from the irradiation port 31 in the cylindrical space T, and the viscosity is sufficiently lowered. A high DC voltage is applied between the electrode 14 and the nozzle 20 from the external power source in the same manner as in FIGS. 1 and 2, and an electric field attractive force is generated in the direction of the conveyor 19. At this time, the nozzle 20 acts as an electrode. The molten resin 28 is drawn in the direction of the conveyor 19 by the electric field attraction, and is accelerated by the air flowing in from the air inlets 13a to 13c by the external compressor, and becomes the ultrafine fiber 10 and reaches the target conveyor 19. . The ultrafine fiber 10 that has reached the conveyor 19 is guided by a deflecting roller driven by a motor (not shown), and is picked up by nip rolls 18a and 18b driven by another motor (not shown) together with the conveyor 19. . Further, it is wound around a bobbin 29 connected to another motor (not shown). At this time, if the rotation speed of the bobbin is sufficiently larger than the yarn speed caused by the electric field and air flow, the bobbin is wound as a single fiber. If the rotation speed of the bobbin is smaller than the yarn speed caused by the electric field and air flow, the bobbin is collected in a web state made of ultrafine fibers. The obtained fiber or web is stretched after the bobbin 29, whereby molecular chains and fibers can be arranged to control physical properties. Further, the air flowing in from the air inlets 13a to 13c is sucked by the suction 17 through the space S and exhausted outside the apparatus.

Among the air inlets 13a, 13b and 13c, the inflow of air from the air inlet 13a by an external compressor is particularly suitable for producing uniform ultrafine fibers. Further, by controlling the amount of air flowing in from the air inlets 13b and 13c, it is possible to stabilize the traveling of the ultrafine fiber 10.
Moreover, you may ventilate with external air, without connecting an external compressor to the air inflow ports 13a, 13b, and 13c.
A plurality of electrodes 14 may be provided. In this case, by changing the voltage applied between the nozzle 20 and each electrode 14, the potential distribution in the cylindrical space T and the distribution of the electric field attractive force can be controlled.
Examples of the laser transmitting material include chalcogenite glass, zinc selenium, silicon, and germanium.

  In the embodiment of FIG. 1, the raw material is a fibrous thermoplastic polymer, infrared is a laser beam, and the target is a collection plate. In the embodiment of FIG. 2, the raw material is a molten resin, the infrared is a light-emitting diode beam, and the target. Is a combination of bobbins. In the embodiment of FIG. 3, the raw material is a combination of molten resin, infrared rays are laser beams, and the target is a conveyor. However, these elements can be implemented in appropriate combinations.

  Hereinafter, although the experiment of the Example to which this invention is applied is demonstrated, the scope of the present invention is not limited to these Experimental examples. Experiments 1, 2 and 3 of the present invention were performed using the apparatus of FIG. Further, Experiment 4 of the present invention was performed using the apparatus of FIG. For comparison, a comparative experiment using melt blow was performed. Here, the maximum temperature of the sample is estimated from the sample temperature before laser irradiation, the output of the laser light source and the output distribution in the laser beam, the cross-sectional area and traveling speed of the sample, the irradiation time, and the density and specific heat of the sample polymer. Value. For estimation, the fact that the fiber temperature rise due to laser irradiation is proportional to the laser output and irradiation time, and inversely proportional to the traveling speed of the fiber. Specifically, first, the fiber is prevented from melting by changing the laser output and the irradiation time or the traveling speed of the fiber from the experimental conditions of the example. In this state, the maximum temperature of the fiber is measured with an infrared thermometer. The maximum temperature in the examples was estimated from the ratio of the obtained temperature and the experimental conditions, that is, laser output, irradiation time, and fiber running speed.

(Experiment 1)
While delivering a polyethylene terephthalate having a diameter of 231.3 ± 4.2 μm at a constant speed, it was heated by laser light irradiation and stretched by an applied voltage to produce ultrafine fibers. The irradiated laser beam is cylindrical and has a beam diameter of 3 mm. Travel speed 0.1 m / sec, orifice-collector distance 50 mm, applied voltage 20 kV, electric field 0.40 kV / mm , laser power 7.0 W, fiber diameter 1.6 μm, maximum sample temperature 440 ° C., irradiation time 0.29 Sec. The estimated maximum fiber temperature is 440 ° C., 190 K higher than the crystal melting temperature of polyethylene terephthalate, 250 ° C. When the laser output was further increased, decomposition progressed and uniform fibers could not be obtained. On the other hand, if the laser output was less than this, fibers with a diameter of 5 microns or less could not be obtained.

(Experiment 2)
A fibrous polyethylene terephthalate having a diameter of 231.3 ± 4.2 μm and a length of 3 mm was heated by irradiation with laser light, and stretched by an applied voltage to produce ultrafine fibers. The irradiated laser beam is cylindrical and has a beam diameter of 3 mm. Sample length 3 mm, orifice-collector distance 65 mm, applied voltage 9.8 kV , electric field 0.15 kV / mm , laser output 11.0 W, fiber diameter 2 μm, sample maximum temperature 480 ° C., irradiation time 0.20 sec. is there. The estimated maximum fiber temperature is 480 ° C., 230 K higher than the crystal melting temperature of polyethylene terephthalate, 250 ° C.

(Experiment 3)
While delivering a fiber-like polyethylene terephthalate having an average diameter of 242 μm at a constant speed, it was heated by laser light irradiation and stretched by an applied voltage to produce ultrafine fibers. The irradiated laser beam has a flat cylindrical shape, and the width in the parallel direction is 1.9 mm and the width in the vertical direction is 9.1 mm with respect to the traveling direction of the fiber. The discharge speed is 0.0004 m / sec, the orifice-collecting plate distance is 50 mm, the applied voltage is 15 kV, the electric field is 0.30 kV / mm , the laser output is 8.5 W, the fiber diameter is 1.8 μm, and the maximum temperature of the sample is 490 ° C. The estimated maximum fiber temperature is 490 ° C., 240 K higher than the crystal melting temperature of polyethylene terephthalate, 250 ° C. When the laser output was increased to 9.1 W or more, decomposition progressed and uniform fibers could not be obtained.

(Experiment 4)
While delivering fibrous polyethylene terephthalate having an average diameter of 242 μm at a constant speed, the fiber was heated by laser light irradiation, and then stretched by air flow and applied voltage to produce ultrafine fibers. The irradiated laser has a flat cylindrical shape, and the width in the parallel direction is 1.9 mm and the width in the vertical direction is 9.1 mm with respect to the traveling direction of the fibers. Discharge speed 0.0004m / sec, orifice-collecting plate distance 50mm, air flow velocity 5m / sec, applied voltage 15kV, electric field 0.30kV / mm , laser power 9.1W, fiber diameter 1.1μm, sample The maximum temperature of 525 ° C. The estimated maximum fiber temperature before acceleration by air flow is 525 ° C., which is 275K higher than the crystal melting temperature of polyethylene terephthalate, 250 ° C.

(Experiment 5)
A fibrous polylactic acid resin having an average diameter of 242 μm and a length of 3 mm was heated by irradiating a laser beam, and stretched by an applied voltage to produce ultrafine fibers. The irradiated laser has a flat cylindrical shape, and the width in the parallel direction is 2.3 mm and the width in the vertical direction is 6.6 mm with respect to the traveling direction of the fibers. The distance between the orifice and the collecting plate is 50 mm, the applied voltage is 15 kV, the electric field is 0.30 kV / mm , the laser output is 8.1 W, the fiber diameter is 0.7 μm, the maximum temperature of the sample is 300 ° C., and the irradiation time is 0.18 sec. The estimated maximum fiber temperature is 300 ° C., 130 K higher than the crystal melting temperature of polyethylene terephthalate, 170 ° C.

(Comparative Experiment 1)
Ultrafine fibers are heated by irradiating laser light to fibrous polyethylene terephthalate with a diameter of 231.3 ± 4.2 μm and a length of 3 mm, and the fibers are stretched by blowing an air stream with Air Spray Hyper Clean 490 (Etsumi). Tried to manufacture. The irradiated laser is cylindrical and has a beam diameter of 3 mm. The sample length is 3 mm, the distance between the orifice and the collecting plate is 70 mm, no voltage is applied, the laser output is 3.5 W, the fiber diameter is 6.6 μm, the maximum temperature of the sample is 454 ° C., and the irradiation time is 0.60 Sec. The fiber temperature calculated from the experimental conditions is 454 ° C., which is 204K higher than the crystal melting temperature of polyethylene terephthalate, 250 ° C. The diameter of the obtained fiber was at least 6.6 μm, and an ultrafine fiber thinner than this could not be produced. When the laser output was further increased, decomposition progressed and uniform fibers could not be obtained. On the other hand, when the laser output was below this, only thicker fibers could be obtained.

It is a figure which shows schematic structure of an example of the apparatus for implementing the ultrafine fiber manufacturing method to which this invention is applied.

It is a figure which shows schematic structure of another example of the apparatus for enforcing the ultrafine fiber manufacturing method to which this invention is applied similarly.

It is a figure which shows schematic structure of another example of the apparatus for enforcing the ultrafine fiber manufacturing method to which this invention is applied similarly.

Explanation of symbols

  1 is a raw material fiber, 3 is a deflection roller, 4a and 4b are nip rolls, 5 is an orifice, 6a and 6b are nip rolls, 7 is a carbon dioxide gas laser, 8 is a reel, 9 is a collecting plate, 10 is an ultrafine fiber, 11 is a laser Beam, 12 is a power source, 13a, 13b, 13c are air inlets, 14 is an electrode, 16 is a vent pipe, 17 is a suction, 18a, 18b, 18c and 18d are nip rolls, 19 is a conveyor, 20 is a nozzle, 22 is an extend Luder, 23 is a hopper, 24 is a screw, 25 is a motor, 26 is an infrared light emitting diode, 27 is a cylinder with a heater, 28 is a molten resin, 29 is a bobbin, 30 is a melt blown die, 31 is an irradiation port, 32 is a laser transmitting material , S is a space portion, and T is a cylindrical space portion.

Claims (11)

Irradiating the thermoplastic polymer melt discharged from the nozzle with infrared rays, the temperature of the thermoplastic polymer melt is raised to a temperature 50 to 500 K higher than the crystal melting temperature or softening temperature of the thermoplastic polymer. And applying a high voltage between the thermoplastic polymer melt sufficiently reduced in viscosity and the target, and accelerating the reduced viscosity thermoplastic polymer melt by applying an air flow, A method for producing ultrafine fibers, characterized in that the thermoplastic polymer melt is spread over the target and thinned to 5 μm or less by attractive force of an electric field of high voltage. The method for producing ultrafine fibers according to claim 1, wherein the temperature of the thermoplastic polymer melt is raised to a temperature 100 to 300K higher than the crystal melting temperature or softening temperature of the thermoplastic polymer. . The method for producing ultrafine fibers according to claim 1, wherein the nozzle is an extruder nozzle . The method for producing ultrafine fibers according to claim 1 , wherein the distance between the nozzle and the target is 2 to 300 mm .   The method for producing ultrafine fibers according to claim 1, wherein the infrared rays are laser beams. Method of producing a ultra fine fiber of claim 5, wherein the laser beam is characterized by a carbon dioxide laser der Turkey. In the cylindrical space where the tip of the nozzle is inserted, an air inlet is provided near one end and the other end, and a melt blow die having a laser beam irradiation port and an electrode sequentially provided below the nozzle. The thermoplastic polymer melt discharged from the nozzle is irradiated with a laser beam from the irradiation port, and a direct current is applied between the electrode and the nozzle while flowing an air flow from the air inlet. The method for producing an ultrafine fiber according to claim 1, wherein an electric field is formed by application . The method for producing ultrafine fibers according to claim 1, wherein the high voltage is 1 to 40 kV , and the average electric field of the high voltage is 0.05 to 1.0 kV / mm .   The method for producing ultrafine fibers according to claim 1, wherein the target is a collection plate, and the ultrafine fibers thinned as described above are randomly captured on the collection plate.   2. The method for producing ultrafine fibers according to claim 1, wherein the target is a bobbin, and the ultrafine fibers that have been thinned as described above are wound around the bobbin. The method for producing ultrafine fibers according to claim 1 , wherein the velocity of the air flow is 0.1 to 500 m / sec, and the temperature of the air flow is 0 to 600 ° C.

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