JP7105508B2 - nanofiber assembly - Google Patents

Description

TECHNICAL FIELD The present invention relates to a nanofiber aggregate suitable for collecting waste oil such as waste oil from tankers and the like and used waste oil from restaurants and the like. In particular, the present invention applies a high-temperature, high-pressure gas from a gas discharge port to a heated polymer melt or a polymer solution dissolved in a solvent (hereinafter sometimes referred to as a "raw material solution") discharged from the solution discharge port. The present invention relates to a nanofiber aggregate produced by a method for producing a nanofiber aggregate, in which a raw material solution is discharged, stretched into fine-diameter fibers, and collected as a nanofiber aggregate.

In this specification, each term is used as meaning as follows.

In the first place, "nano" is a physical unit of metrology, and 1n = 10 ^-9 , and 1000 nm or more is in the micrometer (μm) region, so it is not accurate to call a fiber with a wire diameter of 1000 nm a nanofiber. . However, in this specification, the term "nanofiber" is used as the name of the fiber constituting the nanofiber assembly according to the present invention, even if the fiber has a central fiber diameter exceeding 1000 nm.

Therefore, in the present invention, a heated polymer melt or a polymer solution dissolved in a solvent discharged from a solution discharge port is drawn into a fine-diameter fiber by discharging a high-temperature, high-pressure gas from the gas discharge port. The fiber diameter of the resulting fine fiber group ranges from several tens of nm to several thousand nm, and the term "nanofiber" is used even if the central fiber diameter is from 1000 nm to 2500 nm. In the present invention, for example, nanofibers having a central fiber diameter of 1500 nm and "nanofibers" whose numerical values are quantitatively limited are used.

As used herein, the term “nanofiber assembly” refers to a wire obtained by discharging a high-temperature, high-pressure gas from a gas discharge port to a heated polymer melt or a polymer solution dissolved in a solvent discharged from the solution discharge port. It means an aggregated aggregate obtained by collecting fine-diameter fibers generated and drawn as a fiber stream (hereafter, this fiber stream is called a nanofiber stream).

In this specification, the term "during production and stretching" of nanofibers means that the liquid solution (raw material solution) discharged from the solution outlet is blown away by the wind force of the discharged high-temperature and high-pressure gas, and the high-temperature and high-pressure gas It is used to mean that it is in a region where it is linearly produced from a solution state by wind force, further stretched into fine diameter fibers by wind force of high temperature and high pressure gas, and produced as nanofiber fine diameter fibers. As the high-temperature and high-pressure gas moves away from the discharge port, it spreads in the space. Therefore, the stretching force decreases as the distance from the discharge port increases, and the temperature also decreases, so that the stretching effect of reducing the diameter disappears. The region to which the drawing action of the diameter reduction reaches is used as the region of nanofibers "during generation and drawing".

In the present specification, the term "three-dimensional agitation" means a secondary high pressure to the nanofiber flow being generated and stretched by being ejected from a nanofiber ejection device consisting of a high-temperature, high-pressure gas ejection port and a raw material solution ejection port. By blowing air, the stretching of the fibers during stretching is suppressed to increase the production of nanofibers with a fiber diameter larger than the central fiber diameter of the nanofiber assembly, and at the same time, turbulence is generated in the nanofiber flow, resulting in nanofibers. It means an operation to three-dimensionally stir between fibers.

In the present specification, the “central fiber diameter” of the nanofiber aggregate is the fiber diameter of the centrally distributed fiber in the number distribution of the fiber diameters of the collected nanofiber aggregate. Refers to the most abundant fiber diameter in the body. The "central fiber diameter" of the produced nanofiber aggregate can be adjusted by conditions such as the temperature of the raw material solution, the discharge amount, the discharge speed, and the temperature and pressure of the gas.

As used herein, the term "solution" or "raw material solution" refers to a heated and melted polymer melt discharged from the solution discharge port in the melt blow method, and a polymer dissolved in a solvent in the dry discharge method. Used to refer to both liquids.

As used herein, the term "oil adsorption ratio (OAR)" refers to the ability of nanofiber aggregates to adsorb oil such as waste oil, and is expressed in units of g/g.
The oil adsorption capacity (OAR) is measured according to the following procedure in accordance with Non-Patent Document 1 "Performance Test Standards for Materials for Preventing Oil Discharge".
(i) Measure the dead weight m (g) of a target nanofiber assembly of predetermined size.
(ii) The target nanofiber assembly is entirely immersed in 20° C. oil of viscosity grade ISO VG22 specified by JIS for 5 minutes. The standard of Non-Patent Document 1 stipulated by the Ministry of Land, Infrastructure, Transport and Tourism stipulates that the test should be performed using B heavy oil, but B heavy oil has a large variation in viscosity and is not suitable as a test oil for production control. ISO VG22 defined in JIS equivalent to B heavy oil is used.
(iii) Object (i) was allowed to stand for 5 minutes in a metal net made of a wire with a diameter of 1 mm woven into a mesh with a sieve opening of 17 mm, and then the total weight M (g) of the object aggregate after oil absorption was measured. do.
(iv) Let the oil adsorption capacity (OAR) be OAR=M/m.

As used herein, the term “oil keeping ratio (OKR)” refers to the ability to retain oil such as waste oil adsorbed by nanofiber aggregates while being absorbed, and the unit is g/g. show. The oil retention capacity (OKR) after oil absorption is measured by the following measurement method according to Non-Patent Document 1 "Performance Test Standards for Waste Oil Control Materials". (i) Measure the dead weight m (g) of a target nanofiber assembly of predetermined size. (ii) The target nanofiber assembly is entirely immersed in 20° C. oil of viscosity grade ISO VG22 specified by JIS for 5 minutes. The standard of Non-Patent Document 1 stipulated by the Ministry of Land, Infrastructure, Transport and Tourism stipulates that the test should be performed using B heavy oil, but B heavy oil has a large variation in viscosity and is not suitable as a test oil for production control. ISO VG22 defined in JIS equivalent to B heavy oil is used. (iii) The target (ii) was left for 30 minutes in a metal net made by knitting a wire with a diameter of 1 mm into a mesh with a mesh size of 17 mm, and then the total weight M' (g) of the target nanofiber assembly was Measure. (iv) Let the oil retention capacity (OKR) be OKR=M'/m.

As used herein, the term “bulk density ρ” means the self weight m (g) of the target unit size nanofiber assembly, the volume V (cm ³ ) of the nanofiber assembly, and the “bulk density ” is described as ρ=m/V (g/cm ³ ).

Patent Document 1 (Japanese Patent Application Laid-Open No. 7-275293) is known as a technique for forming and drawing a nonwoven web of substantially continuous fine fibers. US Pat. No. 6,200,000 discloses techniques for providing liquid distribution layers for absorbent articles that exhibit directional liquid distribution properties and have desirable physical integrity. The liquid distribution layer is a substantially continuous fine fiber nonwoven web in which the fibers of the nonwoven web are aligned substantially along one planar surface of the web, and the fibers are modified to be hydrophilic. , or hydrophilic. In addition, the liquid distribution layer has not only an increasing fiber alignment gradient through the thickness of the web, but also a decreasing fiber thickness gradient. Further provided is a suitable process for manufacturing the liquid distribution layer.

Furthermore, Patent Document 2 (Japanese Unexamined Patent Application Publication No. 2013-184095) discloses an oil adsorbent that is excellent in oil adsorption capacity and provides a safe oil adsorbent. Patent Document 2 discloses a nanofiber laminate having a polypropylene fiber diameter of 100 to 500 nm, in which polypropylene is melted by heating it to a high temperature, the melted polypropylene is pressurized and spun from a spinning nozzle, and spun polypropylene. A high-speed, high-temperature air stream is blown in a direction intersecting the propylene fibers so as to stretch the fibers, and the blown-off polypropylene nanofibers are collected and laminated to form an oil adsorbent, a method for producing the same, and an apparatus for producing the same. .

As described above, Patent Document 2 discloses a technique for collecting the nanofiber laminate by blowing the nanofiber laminate to a collection apparatus (net) with respect to the manufacturing method and the manufacturing apparatus. No mention is made of the lamination state of the laminate or other preferred indicators of the nanofiber laminate.

In such a nanofiber aggregate manufacturing apparatus, the liquid solution discharged from the solution discharge port is blown away by the high temperature and high pressure gas discharged from the high temperature and high pressure gas discharge port, and the wind force of the high temperature and high pressure gas changes the solution state into fibers. A manufacturing method and a manufacturing device are generally known in which the nanofiber fiber is generated in a shape, is generated and stretched into a fine-diameter fiber-like fiber fiber, and is collected by a collection device. It is difficult to collect the particles with a uniform thickness over the periphery because they tend to accumulate near the center extension line. Therefore, in the case of commercial use, the nanofiber assembly is processed into a sheet. For example, when it is desired to make an oil adsorbent with high oil adsorption capacity, multiple sheet-shaped nanofiber assemblies are laminated and each sheet-shaped nanofiber There is a problem that processing such as crimping must be performed so that the integrated body does not come off.

JP-A-7-275293 JP 2013-184095 A

"Performance Test Standards for Emission Oil Control Materials" (Notification No. 52 of the Director General of the Ship Bureau, Ministry of Transport dated February 1, 1984

Nanofiber aggregates are used as oil adsorbents, sound-absorbing/insulating materials, heat-insulating/heat-retaining materials, filter materials, and the like, and their uses are known to those skilled in the art. A high oil adsorption capacity (OAR) is desirable when the nanofiber assembly is used for waste oil treatment. Oil adsorption capacity (OAR) simply means the total weight (g) of oil that can be adsorbed per unit weight (1 g) of nanofiber assembly. Since the larger the oil adsorption capacity (OAR), the more oil can be absorbed, a high oil adsorption capacity (OAR) is required. However, for nanofiber aggregates used for waste oil treatment, it is not enough just to have a high oil adsorption capacity (OAR). In particular, nanofiber aggregates used for marine pollution and waste oil treatment are required to have an oil retention capacity (OKR), which retains adsorbed oil for a predetermined period of time even during recovery, as an important capability.

In a method for manufacturing a nanofiber aggregate generally called a dry ejection method or a melt blow method, a raw material solution is ejected from a nanofiber ejection device consisting of a solution ejection port for ejecting a raw material solution and a gas ejection port for ejecting a high-temperature and high-pressure gas. Nanofiber fibers generated and drawn as a linear fiber flow (this fiber flow is called a nanofiber flow) are accumulated and collected by a collection device. Since the discharged nanofiber-like fibers tend to accumulate near the center on the extension line of the high-temperature and high-pressure gas discharge port in the discharge direction, it is difficult to collect them with a substantially uniform thickness from the center to the periphery. Have difficulty. Therefore, when it is used for commercial purposes, the nanofiber assembly is processed into a sheet, and in order to further improve the oil adsorption capacity, multiple sheets of the assembly collected by the collection device are laminated and crimped. It has already been described that the processing must be performed such as

The present invention is intended to solve the above problems, and is excellent in oil adsorption capacity (OAR) and oil retention capacity (OKR), and does not need to be processed into a sheet in a post-process. An object of the present invention is to provide an assembly manufacturing apparatus and a nanofiber assembly having high oil adsorption capacity.

In the method for producing a nanofiber aggregate of the present invention, a nanofiber ejection device having a solution ejection port for ejecting a raw material solution and a high-temperature, high-pressure gas ejection port for ejecting a high-temperature, high-pressure gas ejects from the solution ejection port. By discharging the high-temperature and high-pressure gas discharged from the high-temperature and high-pressure gas discharge port into the raw material solution, the raw material solution is blown off and discharged as a nanofiber flow, and the drawn nanofiber fibers are collected by the collecting device. In the method for manufacturing a nanofiber aggregate, an air blow outlet for additionally discharging high-pressure gas is arranged between the nanofiber discharge device and the collection device, thereby discharging from the nanofiber discharge device. The collection device collects and collects nanofibers obtained by discharging secondary high-pressure air from the air blow discharge port to the flow of nanofibers being generated and stretched.

Further, in the method for producing a nanofiber assembly of the present invention, secondary high-pressure air is discharged to the nanofiber flow being generated and stretched by the nanofiber discharge device, whereby the nanofiber flow to suppress the drawing action to increase the production of nanofibers with a fiber diameter larger than the central fiber diameter of the nanofiber assembly, and at the same time, the nanofiber discharge flow is three-dimensionally stirred, so that the nanofiber fibers The collecting device is characterized in that the nanofibers obtained by entangling are accumulated and collected by the collection device.

An apparatus for manufacturing a nanofiber assembly of the present invention comprises a nanofiber ejection device having a solution ejection port for ejecting a raw material solution and a high-temperature, high-pressure gas ejection port for ejecting a high-temperature, high-pressure gas, and from the high-temperature, high-pressure gas ejection port Manufacture of a nanofiber assembly provided with a collecting device for collecting and collecting nanofibers obtained by generating and stretching the raw material solution discharged from the solution discharge port as a nanofiber flow by the discharged high-temperature and high-pressure gas. The apparatus further comprises an air blow outlet for ejecting high-pressure gas between the nanofiber ejection device and the collection device, and the nanofibers ejected from the nanofiber ejection device and being generated and stretched. It is characterized in that the nanofibers obtained by ejecting secondary high-pressure air from the air blow outlet against the fiber flow are accumulated and collected by the collecting device.

Further, the nanofiber assembly manufacturing apparatus of the present invention discharges secondary high-pressure air to the nanofiber flow being generated and stretched discharged by the nanofiber discharge device, whereby the nanofiber flow turbulent flow is generated in the center of the nanofiber aggregate to suppress the stretching action, thereby increasing the production of nanofibers having a fiber diameter larger than the central fiber diameter of the nanofiber assembly, and at the same time, by three-dimensionally stirring the nanofiber flow, the nanofiber between the fibers The collecting device is characterized in that the nanofibers obtained by entangling are accumulated and collected by the collection device.

The nanofiber assembly of the present invention is characterized by having the following constituent requirements.
(1) the central fiber diameter d is 1000 ≤ d ≤ 2500 (unit: nm);
(2) "bulk density" ρ is ρ≦0.020 (unit: g/cm ³ );
(3) Oil adsorption capacity OAR is OAR≧40 (unit: times),
(4) Oil adsorption and retention capacity OKR is OKR≧40 (unit: times),
(5) The distribution amount of fibers with a diameter smaller than the central fiber diameter d of the nanofiber assembly is greater than the distribution amount of fibers with a diameter larger than the central fiber diameter d.

When a nanofiber flow is generated and drawn by a nanofiber discharge device having a solution discharge port for discharging a raw material solution and a high-temperature/high-pressure gas discharge port for discharging a high-temperature/high-pressure gas, the fiber diameter is not uniformly distributed. A nanofiber aggregate having a desired central fiber diameter is produced under necessary conditions such as the temperature, discharge amount and discharge speed of the raw material solution and the temperature and pressure of the gas. The function of generating and drawing nanofibers is complicated, and as mentioned above, the discharged nanofiber stream does not contain fibers with a uniform diameter, but includes fibers that are thinner than the desired central fiber diameter and fibers that are thicker than the desired central fiber diameter. be However, in addition to the fibers with the desired central fiber diameter, the presence of fibers thinner than the central fiber diameter and fibers thicker than the central fiber diameter will affect the oil adsorption capacity (OAR) and the oil adsorption capacity. (OKR) has been found by the invention of the present application.

In other words, under the necessary conditions such as the temperature, discharge amount and discharge speed of the raw material solution to generate nanofibers with the desired central fiber diameter and the temperature and pressure of the gas, the air blow is applied to the nanofiber flow being generated and stretched. When secondary high-pressure air is blown from the outlet, the fiber is stretched long by the wind force of the high-temperature and high-pressure gas, suppressing the stretching action that makes the diameter thinner, and produces the effect of increasing the diameter of the fiber larger than the desired central fiber diameter. . At the same time, the flow of the nanofibers being generated and drawn is disturbed, producing the effect of sterically entangling the nanofiber fibers, thereby improving the oil adsorption capacity (OAR) and the oil retention capacity (OKR). In particular, when the temperature of the high-pressure air from the air blow outlet is set lower than the temperature of the high-temperature, high-pressure gas, the drawing of the nanofiber fibers during production/drawing increases, and the effect of increasing the number of large-diameter fibers increases. It is preferable that the secondary high-pressure air from this air blow discharge port has a relatively low temperature and is close to room temperature.

Furthermore, if a plurality of air blow outlets for ejecting this secondary high-pressure air are provided, the amount of fibers having a diameter larger than the desired center fiber diameter is increased to improve the oil adsorption capacity (OAR) and the oil retention capacity (OKR). In addition to the effect of improving the strength of the nanofiber aggregate, there is an effect that the shape retention of the aggregate collected by the collection device is enhanced, and the collection can be formed into collectors of various shapes. In the prior art, the nanofibers were gathered in a circular shape around the extension of the high-temperature, high-pressure gas outlet, and the nanofiber aggregate had to be processed into a sheet in a post-process. By discharging, in addition to the effect of increasing the amount of fibers with a diameter larger than the central fiber diameter and improving the oil adsorption capacity (OAR) and oil retention capacity (OKR), sheet-like nano-fibers of a desired shape can be obtained by controlling the air flow rate and direction. An effect that a fiber assembly can be obtained is exhibited.

Schematic diagram of the manufacturing method of the nanofiber assembly of the present invention FIG. 2 is a perspective view showing a nanofiber ejection device and a secondary air blow ejection port assembling device in the nanofiber assembly manufacturing apparatus of the present invention. FIG. 2 is a front view of the nanofiber ejection device and the secondary air blow ejection port assembling device in the nanofiber assembly manufacturing apparatus of the present invention, viewed from the nanofiber collection device side. FIG. 2 is a diagram showing an overall view of a portion that generates and collects nanofibers of the nanofiber assembly manufacturing apparatus of the present invention; FIG. 2 is a perspective view for explaining the details of the nanofiber collecting portion of the nanofiber assembly manufacturing apparatus of the present invention. Appearance photograph of the nanofiber assembly (nanofiber sheet) of the present invention Schematic diagram of another embodiment of the nanofiber assembly manufacturing apparatus of the present invention A diagram showing a specific example of the external shape of a nanofiber assembly that can be manufactured by the method and apparatus for manufacturing a nanofiber assembly of the invention. Fiber diameter distribution diagram (SEM data) comparing nanofiber aggregates produced by the apparatus for producing nanofiber aggregates of the present invention when high-pressure air blowing is stopped and when high-pressure air blowing is in operation. Measured data of the "bulk density" of the nanofiber assembly of the present invention Actual measurement data of OAR and OKR of the nanofiber assembly of the present invention Conceptual diagram of conventional manufacturing method of nanofiber assembly Schematic explanatory view of one example of a conventional nanofiber assembly manufacturing apparatus (melt blow method) Appearance photograph of a nanofiber assembly manufactured by a conventional nanofiber assembly manufacturing apparatus

Hereinafter, the method for producing a nanofiber assembly, the apparatus for producing a nanofiber assembly, and the nanofiber assembly of the present invention will be described more specifically with reference to the drawings. However, the following description with reference to the drawings is merely an explanation of one embodiment of the present invention, and the present invention is not limited by the embodiment, and modifications that can be easily made by those skilled in the art may be made according to the present invention. It is included in the present invention as long as it does not contradict the technical idea of the invention.

In the method for producing a nanofiber assembly of the present invention, a raw material solution is discharged from a solution discharge port by a high-pressure gas discharged from a high-temperature, high-pressure gas discharge port by a nanofiber discharge device comprising a solution discharge port and a high-temperature, high-pressure gas discharge port. is blown away to form a nanofiber flow, and the nanofibers obtained by generation and stretching are accumulated and collected by a nanofiber collection device to manufacture a nanofiber assembly, comprising: a nanofiber ejection device and a nanofiber collection device. By arranging an air blow outlet between the nanofiber collector and the nanofiber collector, secondary high pressure air is discharged from the air blow outlet to the flow of nanofibers being generated and stretched by the nanofiber discharger. It is a manufacturing method characterized by a configuration in which the particles are accumulated and collected.

Further, the method for producing a nanofiber assembly of the present invention is the above-described method for producing a nanofiber assembly, characterized in that a plurality of air blow outlets are provided.

Further, in the method for producing a nanofiber assembly of the present invention, the direction of high-pressure air discharged from at least one of the plurality of air blow outlets is set at an angle with respect to the axial direction of the high-temperature, high-pressure gas outlet of the nanofiber discharger. It is a manufacturing method of the nanofiber aggregate provided with an angle changing means for adjusting.

Furthermore, the method for producing a nanofiber assembly of the present invention is characterized by comprising blowing amount changing means for adjusting the blowing amount of high-pressure air discharged from at least one of the plurality of air blow outlets. A method of manufacturing an aggregate.

Furthermore, the method for producing a nanofiber assembly of the present invention is characterized in that a plurality of air blow outlets are arranged in a circular shape surrounding the flow of nanofibers being generated and stretched by being discharged from the nanofiber discharging device. A method of manufacturing a nanofiber assembly.

Furthermore, the method for producing a nanofiber aggregate of the present invention further includes blowing control means for sequentially controlling the blowing operation of the air blow outlets arranged in the circumferential shape in a clockwise or counterclockwise direction. A method for manufacturing a nanofiber assembly characterized by comprising:

The nanofiber production apparatus of the present invention includes a nanofiber ejection device including a solution ejection port for ejecting a raw material solution and a high-temperature, high-pressure gas ejection port for ejecting a high-temperature, high-pressure gas, and the high-temperature, high-pressure gas is ejected from the ejection port. A nanofiber assembly comprising a collection device for collecting and collecting nanofibers obtained by blowing off the raw material solution discharged from the solution discharge port with a high-temperature, high-pressure gas to form a nanofiber flow, and collecting and collecting the nanofibers produced and drawn. The manufacturing apparatus further includes an air blow outlet for discharging high-pressure gas between the nanofiber discharging device and the collecting device, and the nanofiber discharged from the nanofiber discharging device and being generated and stretched. A nanofiber assembly characterized in that the nanofibers obtained by ejecting secondary high-pressure air from the air blow outlet against the nanofiber flow are accumulated and collected in the collecting device. manufacturing equipment.

In addition, the apparatus for producing a nanofiber aggregate of the present invention is the apparatus for producing a nanofiber aggregate, characterized by comprising a plurality of air blow outlets.

Further, in the apparatus for manufacturing nanofiber aggregates of the present invention, the discharge direction of high-pressure air discharged from at least one of the plurality of air blow discharge ports is set with respect to the axial direction of the high-temperature, high-pressure gas discharge port of the nanofiber discharge device. The apparatus for manufacturing the nanofiber assembly is characterized by comprising an angle changing means for adjusting the angle.

Further, in the nanofiber aggregate manufacturing apparatus of the present invention, the apparatus is characterized by comprising blowing amount changing means for adjusting the blowing amount of high-pressure air discharged from at least one of the plurality of air blow outlets. An apparatus for manufacturing nanofiber aggregates.

Further, the nanofiber assembly manufacturing apparatus of the present invention is characterized in that the plurality of air blow outlets are arranged in a circular shape surrounding the flow of drawing nanofibers discharged from the nanofiber discharger. It is the manufacturing apparatus of the said nanofiber assembly.

Further, the nanofiber assembly manufacturing apparatus of the present invention is characterized in that the plurality of air blow outlets are arranged concentrically with respect to the nanofiber flow discharged from the nanofiber discharge device. It is a body manufacturing device.

Further, the apparatus for manufacturing nanofiber aggregates of the present invention further includes blower control means for sequentially controlling the blowing operation of the air blow outlets arranged in the circumferential shape in clockwise or counterclockwise order. The apparatus for manufacturing the nanofiber assembly is characterized by comprising:

The nanofiber assembly of the present invention is characterized by being a nanofiber assembly having the following constituent requirements.
(1) the central fiber diameter d is 1000 ≤ d ≤ 2500 (unit: nm);
(2) "bulk density" ρ is ρ≦0.020 (unit: g/cm ³ );
(3) Oil adsorption capacity OAR is OAR≧40 (unit: times),
(4) Oil adsorption and retention capacity OKR is OKR≧40 (unit: times),
(5) The distribution amount of fibers with diameters larger than the central fiber diameter d of the nanofiber assembly is greater than the distribution amount of fibers with diameters smaller than the central fiber diameter d

Furthermore, the nanofiber assembly of the present invention is a nanofiber assembly characterized by using polypropylene as a raw material.

Further description will be made below with reference to the drawings. The present invention applies high pressure air from an air blow outlet disposed downstream of the nanofiber discharge device to the nanofiber flow being generated and stretched discharged from the nanofiber discharge device consisting of the raw material solution discharge port and the high-temperature, high-pressure gas discharge port. is ejected to suppress the drawing action of the nanofiber fibers during generation and drawing, and at the same time, the nanofiber flow is three-dimensionally stirred and collected while entangling the nanofiber fibers in the process up to the collection device. By accumulating on the collection surface of the device, the porosity is increased and the nanofiber aggregates with low "bulk density" are accumulated and collected in a predetermined shape such as a sheet, mat, or block to solve the problem. .

Although the present invention can be applied to both the dry spinning method (using a solution) and the melt blowing method (using a molten raw material), the melt blowing method will be described below as a representative example. Generally, nanofiber production called the meltblowing method is performed by the method shown in the conceptual diagram of FIG. 12 . A high-temperature, high-pressure gas 220 is discharged from the high-temperature, high-pressure gas discharge port 22 to the melted polymer solution 210 discharged from the raw material solution discharge port 21 (a combination of the raw material solution discharge port 21 and the high-temperature, high-pressure gas discharge port 22 This device is referred to as a nanofiber discharging device 2.) A nanofiber stream 40 is discharged from the raw material polymer in the form of droplets, and collected by a collection device 9 through a nanofiber generation/stretching region. FIG. 13 shows an example of a manufacturing apparatus embodying the conceptual diagram of FIG.

FIG. 13(A) is a perspective view showing a specific example of a nanofiber assembly manufacturing apparatus, and FIG. 13(B) is a side sectional view of the apparatus of FIG. 13(A). The nanofiber assembly manufacturing apparatus 50 has a hopper 62 , a heating cylinder 63 , a heater 64 , a screw 65 , a motor 66 and a nanofiber discharging device 2 .

The hopper 62 is charged with a pellet-shaped synthetic resin as a raw material for producing nanofibers. Heated by the heating cylinder 63 and the heater 64, the resin supplied from the hopper 62 is melted. The screw 65 is housed within the heating cylinder 63 . A screw 65 is rotated by a motor 66 to send the molten resin to the tip of the heating cylinder 63 . A high-pressure gas supply unit (not shown in this figure) is connected via a gas supply pipe 68 to the cylindrical nanofiber discharge device 2 in which the resin discharge port 21 and the high-temperature, high-pressure gas discharge port 22 are accommodated. It is The gas supply pipe 68 is equipped with a heater to heat the high pressure gas supplied from the gas supply pipe to a high temperature. The nanofiber discharge device 2 discharges the molten resin so as to ride on the high temperature and high pressure gas flow, that is, discharges the nanofiber flow. Naturally, in a dry spinning method using a solution as a raw material to be discharged, such a structure for melting the resin is unnecessary. A collection device 9 is arranged in front of the nanofiber discharging device 2, and the nanofibers are accumulated and collected by this collection device 9. As shown in FIG.

The nanofiber assembly produced in this manner is flocculate as shown in FIG. 14, and has a shape in which a large amount of nanofiber flow 40 is accumulated in the central portion shown in FIG. It is generally used as a nanofiber laminate by stretching it into a sheet and laminating a plurality of sheets.

FIG. 1 shows a conceptual diagram of the method for producing a nanofiber assembly of the present invention. In addition, in the process of producing and drawing nanofibers, the conceptual diagram is the same for both the melt blowing method and the dry spinning method. The nanofiber ejection device 2 ejects a high-temperature, high-pressure gas from a high-temperature, high-pressure gas ejection port 22 to a melted polymer resin material or a dissolved polymer resin material (raw material solution) ejected from a raw material solution ejection port 21. , the raw material solution is discharged and stretched as a nanofiber stream 40 to generate nanofibers. This conceptual diagram seems to be similar to FIG. 12 in the conventional example, but in the present invention, the flow of the nanofibers being generated and stretched discharged from the nanofiber discharger 2 is It is characterized by having an air blow outlet 17 that secondarily discharges high-pressure air for suppressing the drawing action of the fibers and at the same time disturbing the flow of the nanofibers to three-dimensionally agitate the nanofiber fibers. In this way, when high-pressure air is discharged from the air blow outlet 17 to cross the flowing nanofiber stream 40 discharged from the nanofiber discharge device 2, the nanofiber stream is disturbed and the nanofiber fibers being generated and stretched are disturbed. At the same time, the nanofiber flow can be three-dimensionally stirred and the fibers can be entangled with each other intricately. Furthermore, by providing a plurality of air blow outlets 17 around the nanofiber flow and individually controlling and collecting all or part of the nanofiber flow from these air blow outlets, the collection device 9 The purpose was to be able to form and collect a nanofiber sheet with a desired shape.

2 to 5 show an example of a manufacturing apparatus embodying the conceptual diagram of the manufacturing method of the nanofiber assembly of the present invention shown in FIG. It is a diagram showing so as to understand the relationship between.

FIG. 2 is a perspective view showing the arrangement relationship between the nanofiber ejection device 2 and the air blow ejection port 17. As shown in FIG. FIG. 3 is a perspective view of the nanofiber ejection device 2 viewed from the front of the air blow ejection port 17 attachment side (right side of FIG. 2) in the perspective view of FIG. As can be seen from FIGS. 2 and 3, a plurality of air blow outlets 17 are arranged so as to surround the outlet of the nanofiber ejection device 2 . Although the nanofiber flow 40 is not shown in this figure, the air blow outlet 17 is arranged so as to surround the nanofiber flow 40 discharged from the nanofiber discharge device 2 . The air blow outlet 17 is attached and fixed to the holding frame 19, and the air outlet angle of the air blow outlet 17 is adjusted with respect to the axial direction of the high-temperature and high-pressure gas outlet 22 by means of an angle adjustment plate (air nozzle blowing angle changing means) 18. It is configured to A plurality of air blow outlets 17 shown in FIG. 3 and the angle adjustment plates 18 of the respective air blow outlets 17 are integrated with a holding frame 19 to form a subassembly, which is hereinafter referred to as an air blow outlet assembling device 170 having this subassembly. It is assumed that

FIG. 4 is a diagram showing an example of a nanofiber assembly manufacturing apparatus embodying the conceptual diagram of the nanofiber assembly manufacturing method of the present invention shown in FIG. FIG. 4 is a diagram showing the relative positional relationship of the nanofiber discharge device 2, the air blow discharge port assembly device 170, and the collection device 9. In order to make the whole device easy to understand, the size of each device and the distance between devices Shown not to scale.

Nanofiber stream 40 ejected from nanofiber ejection device 2 in FIG. When high-pressure air is discharged from a plurality of air blow discharge ports 17 incorporated in the air blow discharge port assembling device 170 and intersects the nanofiber flow 40 being generated and drawn, the drawing action is exerted on the nanofiber fibers being generated and drawn. At the same time, the flow of nanofibers is disturbed, and the nanofiber fibers are three-dimensionally entangled with each other and collected by the collection device 9 .

In particular, when the temperature of the high-pressure air discharged from the air blow discharge port 17 is lower than the temperature of the high-temperature high-pressure gas 220 discharged from the high-temperature high-pressure gas discharge port 22 in the nanofiber discharge device 2, the high-pressure air is generated at the time of intersection.・The effect of increasing the amount of fibers with a diameter larger than the central fiber diameter can be expected because the drawing action of the nanofiber fibers during drawing stops. The temperature of the high-pressure air discharged from the air blow outlet 17 is set relatively low, preferably close to room temperature.

The collecting device 9 shown in FIG. A scraping means drive motor (not shown) is provided to drive the scraping means. The collecting means rotating shaft 4 is stopped each time it is rotated by 90°, and a rotation control means (not shown) rotates the scraping means rotating shaft 5 by 360° immediately after the collecting means rotating shaft 4 is stopped. Prepare. The nanofiber stream 40 discharged from the nanofiber discharging device 2 passes through the air blow outlet assembling device 170 and is discharged from a plurality of air blow outlets 17 attached to the air blow outlet assembling device 170 with high pressure air. While being three-dimensionally stirred, the particles are accumulated and collected by the collecting means 3 stopped at the lower position. The nanofiber aggregates F collected and collected by the collecting means 3 are rotated by 45° in the M direction and the scraping means rotating shaft 5 is rotated in the N direction. It is scraped off by a U-shaped scraping bar 12 attached to the shaft 5 . As already described above, the collecting means driving motor, the scraping means driving motor, and the rotation control means are not essential to the essence of the present invention, and are therefore not shown.

FIG. 5 shows details of the collection means 3 inside the nanofiber collection device 9 . The collecting means rotating shaft 4 is provided with 11 parallel collecting rods 3 arranged in the axial direction of the collecting means rotating shaft 4 . Each of the parallel collection rods 3 is provided at its tip with a fall prevention portion 10 that is bent and extended.

4 and 5, the eleven parallel collecting rods 3, which are the nanofiber collecting means of this embodiment, are provided in four directions on the outer periphery of the collecting means rotating shaft 4. As shown in FIGS.

As shown in FIG. 5, a U-shaped predetermined shape holding member 11 is fixed to each of the 11 parallel collection rods 3 located at both left and right ends. The predetermined shape holding member 11 and the drop-off prevention part 10 described above are arranged so that the nanofiber aggregate F collected by the parallel collection rod 3 protrudes outside the parallel collection rod 3 due to the centrifugal force caused by the rotation. Prevents falling off.

As shown in FIG. 4, both ends of a U-shaped scraping rod 12 are fixed to the scraping means rotating shaft 5 . There are 11 parallel collecting rods 3 provided on the collecting means rotating shaft 4, and the intervals between the parallel rods 3 are 10 spaces. The space in which the taking rod 12 can rotate is 8 spaces. In order to scrape the nanofiber aggregates F accumulated and collected by the collecting means 3, the U-shaped scraping rods 12 do not have to be provided in all eight spaces, and there is no problem even if there are eight or less.

The scraping rods 12 pass through the gaps between the parallel collecting rods 3 and are collected by the eleven parallel collecting rods 3 when the scraping means rotating shaft 5 is rotated 360° by the rotation control means. The nanofiber assembly F that has been applied is stripped off. In addition, a recovery container 13 is installed below the nanofiber assembly F stripped off from the parallel collection rod 3, and the nanofiber assembly F stripped off from the parallel collection rod 3 is recovered by its own weight. It is automatically collected in container 13 .

In this embodiment, when the parallel collection rods 3 are arranged on the front, back, top and bottom of the outer periphery of the collecting means rotating shaft 4, the rotation control means stops the rotational driving of the collecting means rotating shaft 4 (state shown in FIG. 4). ). Then, the nanofiber stream 40 is discharged from the discharge nozzle of the nanofiber discharge device 2 only to the parallel collection rod 3 positioned below the collection means rotating shaft 4, and the parallel collection rod 3 is rotated by 90° from there and placed horizontally, the scraping means rotating shaft 5 is rotated by 360°, and the scraping rod 12 moves along with the nanofibers collected by the parallel collection rod 3. The aggregate F is stripped off. Then, the nanofiber assembly F that has been stripped off is automatically recovered in the recovery container 13 .

Next, for the nanofiber flow 40 discharged from the air blow discharge port 17 and the nanofiber discharge device 2, which are the embodiments of the present invention, the drawing action of the nanofiber fibers being generated and drawn is suppressed, and at the same time, the nanofiber flow is suppressed. An air blow outlet assembling device 170 for disturbing the fiber flow 40 and sterically entangling the nanofiber fibers will be described in detail below with reference to FIGS. The air blow assembly device 170 of the present embodiment needs to be installed between the nanofiber discharge device 2 and the collection device 9, but even if it is installed accompanying the nanofiber discharge device 2, it can be installed independently. You can

The plurality of air blow outlets 17 mounted on the air blow outlet assembling device 170 are generated by applying disturbance to the nanofiber flow discharged from the nanofiber discharge device 2 by applying high pressure air from the surroundings of the nanofiber flow. Arranged in a manner surrounding the nanofiber stream 40 (not shown in this figure) to suppress the drawing action of the nanofiber fibers during drawing and at the same time sterically disturb the nanofiber stream and cause the fibers to become intricately entangled with each other. is doing. In this embodiment, the air blow outlets 17 are arranged on the circumference so as to surround the nanofiber flow 40 (not shown in this figure). It doesn't have to be on top.

The air blow outlet 17 can be adjusted in angle with respect to the axial direction of the high-temperature, high-pressure gas outlet by means of an angle adjusting plate 18 . The angle adjustment plate 18 is mounted on a hollow disk-shaped holding frame 19 so as to be slidable in the radial direction (the direction toward or away from the discharge flow of the nanofiber flow). A pipe or the like for supplying high-pressure air is required for the air blow discharge port 17, but the pipe or the like is not shown for simplification. These pipes can lead high-pressure air to the air discharge port 17, and in addition to the pipes, a pump and a solenoid valve for turning on/off the supply of high-pressure air are provided. is possible, and detailed description is omitted in this specification. In the embodiment of the present invention, air blow control means 50 for controlling various air blowing operations in addition to the discharge time of each air blow outlet 17 and air blow amount changing means 51 for electrically adjusting the air blow amount of the air nozzle 17 are provided. .

A hollow disk-shaped holding frame 19 with a plurality of air blow outlets 17 mounted in a circumferential shape is located downstream of the nanofiber outlet 2 so as to surround the nanofiber flow 40 ejected from the outlet 2. are placed. It is configured integrally with the nanofiber ejection device 2 via a connecting frame (not shown in the figure). As shown in FIGS. 2 to 4, eight air blow outlets 17 are arranged concentrically at equal intervals (45° intervals) around the arrangement of the nanofiber outlets 2. Of course, the plurality of air blow outlets 17 need not be concentric, and the arrangement is not limited to eight at intervals of 45°.

Each air blow outlet 17 is attached to the holding frame 19 via an angle adjustment plate 18 . The angle adjustment plate 18 is structured to be slidable in the direction toward or away from the nanofiber flow, that is, in the radial direction on the hollow disk-shaped holding frame 19. A blowing angle changing means for adjusting the blowing direction angle from the air blow outlet 17 is also provided. Although this drawing does not refer to the method of adjusting the sliding mechanism and the air blowing angle adjusting means in the radial direction on the holding frame 19 of the angle adjusting plate 18, it goes without saying that this can be done manually or automatically using a control device. no.

The method for producing a nanofiber assembly of the present invention employs a method for producing a nanofiber assembly by generating and stretching the nanofiber flow 40 discharged from the nanofiber discharge device 2 and collecting and collecting the nanofiber flow 40 with a collection device. High-pressure air is discharged from the air blow outlet 17 against the nanofiber flow 40 being generated and drawn discharged from the nanofiber discharging device 2, and the nanofiber fiber being generated and drawn is stretched. In this method, three-dimensional entanglement between nanofiber fibers is accelerated by suppressing and three-dimensionally stirring the nanofiber flow 40 at the same time. By controlling the direction, it is possible not only to accelerate the three-dimensional entanglement between the nanofiber fibers, but also to change the nanofiber accumulation direction to obtain a nanofiber aggregate having a desired shape.

FIG. 6 shows a photograph of a square sheet-like nanofiber aggregate produced by the production apparatus of the present invention. As can be seen from this figure, the nanofibers are aggregated on average over the entire surface of the square, and unlike the case of the aggregate produced by the conventional production method shown in FIG. It can be seen that it is not necessary to form a sheet in the process.

In the case of an air blow outlet assembling device 170 in which a plurality of air blow outlets 17 are assembled, the individual air blow outlets 17 or blocks or the entire air blowing operation is performed continuously clockwise or counterclockwise in order, or randomly. to control airflow. The blowing control in this case may be on/off control of the blowing of each air blow outlet 17 or control of the blowing amount. As a result, the air is controlled by the plurality of air blow outlets 17 to suppress the stretching action of the nanofiber fibers being generated and stretched, and at the same time, the nanofiber flow 40 is three-dimensionally agitated to three-dimensionally entangle the nanofiber fibers. , the entire nanofiber stream 40 can be three-dimensionally agitated and confined from the surroundings, and the nanofiber stream can be manufactured into a desired shape for accumulation. Thereby, a nanofiber assembly having a desired shape can be manufactured.

FIG. 7 is a conceptual diagram of another embodiment of the nanofiber manufacturing apparatus of the present invention, in which two sets of air blow outlets surrounding the nanofiber flow 40 are placed between the nanofiber discharge device 2 and the nanofiber accumulation/collection device 9. It is a diagram equipped with assembling devices 171 and 172. By doing so, it is possible to share the roles of three-dimensional stirring of the nanofiber flow and accumulation molding, and to further freely control the shape of the nanofiber accumulation.

According to the nanofiber assembly manufacturing apparatus of the present embodiment as described above, high-pressure air is appropriately adjusted to be discharged from the plurality of air blow outlets 17 into the nanofiber discharge stream 40, thereby accumulating and collecting in the nanofiber collection means. It is possible to freely collect and collect the collected nanofiber aggregates F in a shape such as a square, rectangle, or round shape shown in FIG. As a result, it is possible to form a sheet-like, mat-like, or block-like predetermined shaped body. Also, the nanofiber aggregates F can be uniformly accumulated on the spraying surface of the parallel collection rod 3 regardless of the accumulation amount.

FIG. 9 shows fiber diameter distribution data obtained by examining a nanofiber assembly having a central fiber diameter of 1500 nm produced by the nanofiber assembly production apparatus of the embodiment of the present invention shown in FIG. 4 with a scanning electron microscope (SEM). . The measurement of the fiber diameter is carried out by cutting the nanofiber assembly produced by the production apparatus of the embodiment of the present invention into a test piece of about 10 mm x 5 mm square, and measuring the fiber diameter of the nanofiber assembly constituting the test piece. did. A scanning electron microscope (SEM) was used to measure the fiber diameter distribution at 300 different points in the test piece, and the results were totaled and averaged.

For comparison, FIG. 9(A) shows the distribution of the fiber diameter of the nanofiber assembly produced by stopping the discharge of high-pressure air from the air blow discharge port 17 using the apparatus of the embodiment of the present invention. there is FIG. 9B shows the fiber diameter distribution of the nanofiber assembly of the present invention manufactured by discharging high-pressure air from the air blow outlet 17 as an example of the present invention, and the fiber diameter distribution of FIG. 9A. The difference is shown in comparison. In both FIGS. 9(A) and 9(B), the width of the horizontal axis of one bar indicates the 120 nm band, and the vertical axis indicates the fiber diameter of 1500 nm, which is the central fiber diameter (the most frequently occurring fiber diameter). , the number of fibers within the 120 nm bandwidth (1440 to 1560 nm) is normalized to 1.0, and the other is the number of fibers within each 120 nm band (not the number of fibers, but the fiber FIG. 10 is a diagram showing the ratio of the frequency of occurrence of diameters.

As can be seen from the comparison of FIGS. 9A and 9B, high-pressure air is discharged from the air blow outlet 17 compared to the nanofiber assembly manufactured without discharging high-pressure air from the air blow outlet 17. It was confirmed that the nanofiber assembly of the present invention produced by the above method has a wide distribution band of fiber diameters, and in particular, has a large amount of fibers having diameters larger than the central fiber diameter. This comparative data suggests that the high-pressure air discharged from the air blow outlet 17 widens the distribution band of the nanofiber fiber diameters and increases the large diameters of the fibers. Thus, it can be considered that the high-pressure air discharged from the air blow outlet 17 suppresses the stretching of the nanofiber fibers that are generated and stretched by being discharged from the nanofiber discharge device 2 . In other words, it is a natural result that the secondary air disturbance that suppresses the diameter reduction by drawing does not progress and the generation of thicker nanofibers increases. I can say The increase in the number of fibers with a large fiber diameter means that the aggregate becomes bulky in a sense, and because the space between the nanofiber fibers increases, the amount of oil that the accumulated nanofiber aggregates can absorb increases. It can be understood that the connection enhances the oil adsorption capacity of the nanofiber assembly of the present invention.

In the nanofiber assembly of the present invention, the amount of fibers having a diameter larger than the central fiber diameter increases, and the thicker fibers are three-dimensionally and complicatedly entangled with each other, resulting in an increase in the space between the nanofiber fibers. The increase in the space between these nanofiber fibers leads to an increase in the space that can absorb oil, and at the same time, it is expected that the ability to retain the absorbed oil will be improved due to the increase in the thick fiber diameter. can. In other words, the nanofiber assembly produced by the nanofiber production apparatus according to the present invention has the effect of improving oil adsorption capacity and oil retention capacity after oil adsorption.

In the nanofiber assembly of the present invention, the distribution amount of fibers having a diameter larger than the central fiber diameter is equal to or greater than the distribution amount of fibers having a diameter smaller than the central fiber diameter, and the nanofiber fibers are sterically entangled. It is characterized by an increase in voids, but it is due to the method of measuring the fiber diameter distribution with a scanning electron microscope (SEM) shown in FIG. Since the method of measuring the porosity and using it as a control index is not practical, in the present invention, instead of the control index, the "bulk density" is used as the performance control index. "Bulk density" is weight divided by volume, and the porosity, which is related to the fiber diameter distribution and the degree of entanglement between fibers, is inversely proportional to this "bulk density." indicates that the porosity is high, so it can be said to be a rational management index representing the nanofiber assembly of the present invention.

As described above, the "bulk density" is obtained by dividing the weight m (g) of the nanofiber assembly by the volume V (cm ³ ). The measurement method defined "bulk density". The measurement of "bulk density (symbol ρ)" is performed on a sheet-like nanofiber aggregate of a predetermined size as follows. Since commercially available oil adsorbents are generally in the form of sheets of 30 cm square or 50 cm square,
(i) Cutting and dividing the sheet-like nanofiber assembly into 9 square pieces of 3 × 3 (ii) Overlapping the 9 pieces of (i) in a square bottom shape transparent case with one side length plus 1 cm (iii) 9 Measure the net weight W (unit: g) of the nanofiber assembly of the piece (iv) Measure the height H (unit: cm) stacked in (ii) (v) Nanofiber area S (unit: cm) of one piece ² )
(vi) Bulk density ρ = W/(S H) (unit: g/cm ³ )

FIG. 10 shows a table showing the measurement results of the "bulk density" of the nanofiber assembly of the present invention. 89 nanofiber aggregates of the present invention having a central fiber diameter of 1500 nm in a sheet shape of 30 cm square shown in FIG. Results show minimum, mean, maximum and standard deviation.

Considering FIG. 10, the nanofiber assembly of the present invention having a central fiber diameter of 1500 nm has an average "bulk density" of 0.012 (g/mm ³ ) and a standard deviation of 0.002 (g/mm ³ ). According to the method for producing a nanofiber assembly and the apparatus for producing a nanofiber assembly of the present invention, a nanofiber assembly having a very stable and low "bulk density" of 0.020 or less can be obtained. can be produced.

FIG. 11 is data obtained by measuring the oil adsorption capacity (OAR) and the oil retention capacity (OKR) of the nanofiber assembly of the present invention having a central fiber diameter of 1500 nm shown in FIG. The oil adsorption capacity (OAR) and oil retention capacity (OKR) of the nanofiber assembly of the present invention are 40 times or more superior, which is significantly higher than that of commercial products.

Although the present invention has been described in detail above, the manufacturing method and manufacturing apparatus of the nanofiber assembly of the present invention is provided with a secondary air blow outlet between the nanofiber discharge device and the collection device to discharge the nanofibers. High-pressure air is discharged from the air blow outlet against the flow of nanofibers discharged from the device, suppressing the stretching action of the nanofibers being generated and stretched, stably accumulating nanofiber aggregates with low "bulk density". It is characterized by collecting. In addition, the temperature, air volume, wind force, and discharge angle of the high-pressure air are automatically adjusted individually or in groups by a control device, so that the collected nanofibers of the present invention can be collected in a uniform shape. It is characterized by high oil adsorption capacity and oil retention capacity due to its high fiber content and low "bulk density".

In the present specification, an example in which the nanofiber assembly of the present invention is applied to an oil adsorbent by focusing on the oil adsorption capacity of the nanofiber assembly of the present invention has been described, but the application of the nanofiber assembly of the present invention is not limited to oil adsorbents. . The nanofiber assembly of the present invention is widely distributed from small diameter to large diameter at the center of the average fiber diameter, and in particular, contains a wide range of fibers that are thicker than the average fiber diameter, and the nanofiber fibers are sterically entangled and the nanofiber fibers are separated. It is characterized by an increase in space, and although not described in detail in this specification, a low "bulk density" and a high porosity mean that it has excellent sound absorption performance and heat insulation performance. Needless to say, it is a suitable material for soundproofing materials, heat insulating materials, heat retaining materials, and other widely known uses of ultrafine fibers.

2 nanofiber ejection device 3 parallel collection rod (nanofiber collection means)
4 Collecting means rotating shaft 5 Scraping means rotating shaft 9 Nanofiber collecting device 10 Falling prevention part 11 Predetermined shape holding member 12 Scraping bar 13 Collection container 17 Air blow outlet 170 Air blow outlet assembling device 18 Deflection angle adjustment plate ( Means for changing the blowing angle of the air outlet)
19 Holding frame 21 Raw material solution outlet 210 Raw material solution 22 High temperature and high pressure gas outlet 220 High temperature and high pressure gas 40 Nanofiber flow discharged from the nanofiber discharge device 50 Air blow amount changing means 51 Air blow control means (control means)
F nanofiber assembly

Claims (2)

A nanofiber assembly characterized by having the following constituent requirements.
(1) The central fiber diameter d, which is the fiber diameter most contained in the number distribution of the fiber diameters of the collected nanofiber assembly, is 1000 ≤ d ≤ 2500 (unit: nm),
(2) "bulk density" ρ is ρ≦0.020 (unit: g/cm ³ );
(3) The oil adsorption capacity OAR for oil of viscosity grade ISO VG22 defined in JIS at 20 ° C. is OAR ≥ 40 (unit: times),
(4) The oil adsorption retention capacity OKR for oil at 20 ° C. of viscosity grade ISO VG22 specified in JIS is OKR ≥ 40 (unit: times),
(5) The distribution amount of fibers with diameters larger than the central fiber diameter d of the nanofiber assembly is greater than the distribution amount of fibers with diameters smaller than the central fiber diameter d. The nanofiber aggregate according to claim 1,
A nanofiber aggregate, characterized in that the raw material is polypropylene.

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