JP6489297B2 - Manufacturing method of three-dimensional structure and three-dimensional structure - Google Patents

Description

  The present invention relates to a three-dimensional structure of nanofibers and a method for producing the same.

In recent years, fibers having a fiber diameter of less than 1 μm, that is, in the nanometer (several nanometers to several hundreds nanometers) range have attracted attention in a wide range of fields such as biotechnology and environmental fields. As a means for producing the nanofiber, an electrospinning method (hereinafter sometimes abbreviated as ES method) is representative. However, this ES method requires the polymer to be dissolved in a solvent, and the product that is produced also requires desolvation. Therefore, the production method is complicated, and there is no molecular orientation of the filament. There were many problems in terms of quality, such as small masses of resin called lumps and shots mixed in the aggregate.
The nanofiber structure by the ES method is disclosed in, for example, Patent Documents 1, 2, and 3. However, as a feature of the ES method, it is clogged in the bulk direction and the dispersibility of the voids is not uniform. If it is not a soluble polymer, it has a problem that it cannot be produced.

JP 2006-312794 JP JP 2006-328562 A JP 2008-261064

  An object of the present invention is to make a three-dimensional structure of nanofibers excellent in dispersibility of voids, and further to obtain a three-dimensional structure of ultrafine filaments in the nanofiber region by simple means. is there. Furthermore, the present invention includes polyesters such as polyethylene terephthalate and polyethylene naphthalate, biodegradable polymers such as polylactic acid and polyglycolic acid, and fluorine-based polymers such as tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA). An object of the present invention is to provide a three-dimensional structure that can be used for various purposes such as medical use and filters with respect to nanofilaments obtained from thick filaments.

In the three-dimensional structure of the present invention, voids are formed by long fibers of nanofilaments having a filament diameter of less than 1 μm.
A three-dimensional structure is manufactured by accumulating nanofilaments composed of one or a plurality of long fibers, collected in a cotton shape, and placing the cotton-like nanofilament in a mold, followed by heat compression molding. The
Moreover, the heat compression molding by a metal mold | die can be heat compression molding, after mixing the excipient | filler which can be removed after shaping | molding with a nanofilament.
At this time, an inorganic salt can be used as the excipient.
Further, the nanofilaments to be accumulated are supplied to the orifice under the P1 atmospheric pressure by the original filament delivered by the filament delivery means, and the difference in atmospheric pressure before and after the orifice is P1 ≧ 2P2 in the extending portion under the P2 atmospheric pressure. It is guided and manufactured by a supersonic stretching method in which the stretched portion is heated and stretched by an infrared light beam.
The original filament in the present invention is already manufactured as a filament and wound on a reel or the like. In the spinning process, the melted or melted filaments that have become filaments by cooling or coagulation are subsequently used in the spinning process and become the original filament of the present invention. Here, the filament is a substantially continuous fiber, and is distinguished from a short fiber having a length of several millimeters to several tens of millimeters.
In the present invention, all the filaments drawn are expressed as filaments, but those that belong to the fiber region as a result of drawing are also included. In most cases, the stretched filament in the present invention is stretched for several minutes without being stretched. Therefore, considering that the length of the filament is several meters or more and the filament diameter d is small, it is substantially continuous. In most cases, it can be regarded as a filament.

  The original filament in the present invention is characterized in that a highly molecularly oriented filament having an orientation degree measured by birefringence of 30% or 50% or more can be used. Thus, when the original filament is highly oriented, it is often drawn with an expanded portion that is larger than the original filament diameter at the drawing start point.

  The raw filament of the present invention includes polyethylene terephthalate, polyester containing aliphatic polyester and polyethylene naphthalate, polyamide including nylon (including nylon 6, nylon 66), polyolefin including polypropylene and polyethylene, polyvinyl alcohol polymer, acrylonitrile polymer, Use filaments made of thermoplastic polymers such as fluoropolymers including tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), vinyl chloride polymers, styrene polymers, polyoxymethylene, ether ester polymers can do. In particular, polyethylene terephthalate, nylon (including nylon 6, nylon 66) and polypropylene have good stretchability and good molecular orientation, and are particularly suitable for the production of the three-dimensional structure of the ultrafine filament of the present invention. In addition, biodegradable polymers such as polylactic acid and polyglycolic acid, biodegradable and absorbable polymers, and high-strength and high-elastic polymers such as polyarylate and aramid also have good stretchability by the infrared beam of the present invention. It is particularly suitable for the production of a three-dimensional structure using ultrafine filaments according to the invention. In addition, composite filaments such as core-sheath filaments made of these polymers can also be used as the original filament. When the polymer is contained in an amount of 85% (weight percent) or more, it may be expressed as a polyester “system” or a polyester “main component”.

In the present invention, the original filament sent out from the filament sending means is stretched. As the delivery means, various types can be used as long as the filament can be delivered at a constant delivery speed, such as a combination of a nip roller and several stages of driving rollers. When it is desired to stretch only a certain length of filament, the original filament may be gripped by a chuck, lowered at a constant speed, and supplied to the orifice.
The original filament sent out from the filament delivery means is further sent through the orifice and by the gas flowing in the original filament in the traveling direction. Until the original filament is sent to the orifice through this filament delivery means, it is performed in an atmosphere of P1 atmospheric pressure, and the place kept under the P1 atmospheric pressure is defined as the original filament supply chamber.

  After the outlet of the orifice, it is maintained at P2 atmospheric pressure, and becomes a drawing chamber that is drawn by heating the original filament that has come out of the orifice with infrared rays. The original filament is sent through the orifice by the flow of air flowing through the orifice caused by the pressure difference (P1-P2) between the original filament supply chamber at P1 atm and the stretching chamber at P2 atm. When P2 is at atmospheric pressure, an enclosure that keeps the pressure constant is not particularly necessary. However, when P2 is under pressure or pressure reduction, an enclosure (room) is required to maintain the pressure. A vacuum pump is also required. At this time, the pressure difference between P1 and P2 is P1> P2.

  In the present invention, it is particularly desirable that P2 is performed under reduced pressure (pressure less than atmospheric pressure). By doing so, P1 can be carried out at atmospheric pressure, the apparatus can be remarkably simplified, and reduced pressure is a relatively simple means. In addition, since air is ejected from the orifice under reduced pressure, it is not disturbed by the atmospheric air that normally exists, so the air that is ejected and the filament that accompanies it are very stable. It seems that the properties are stable, and it is possible to stretch to the nanofilament region. In addition, normally, when high-speed fluid is ejected from the nozzle, a large amount of accompanying flow is generated around the nozzle, but under reduced pressure, this accompanying flow is also reduced, so as not to disturb the flow of the filament emitted from the nozzle. It seems to enable stable stretching.

  In the present invention, the original filament supply chamber and the drawing chamber are connected by an orifice. In the orifice, a high-speed gas flow generated by a pressure difference of P1> P2 is generated in a narrow gap between the original filament and the inner diameter of the orifice.

  In the present invention, stretching is preferably performed in the sonic range, and by setting the wind speed in the stretching chamber to the sonic range, it was possible to obtain an ultrafine filament having a filament diameter of up to the nanometer range obtained by stretching. .

The original filament sent out from the orifice is heated by the infrared light beam at the exit of the orifice, and the original filament is drawn by the tension applied to the filament by the high-speed fluid from the orifice. “Directly under the orifice” means that the center of the infrared light beam is 30 mm or less, preferably 10 mm or less and 5 mm or less from the orifice tip. This is because when the filament is separated from the orifice, the original filament swings and does not stay in a fixed position, and cannot be stably captured by the infrared light beam. Further, it is considered that the tension applied to the filament by the high-speed gas from the orifice is weakened by moving away from the orifice, and the stability is also reduced.
The present invention is characterized in that the original filament is heated and stretched by an infrared light beam. Infrared rays have a wavelength of 0.78 μm to 1 mm, but the C—C bond of the polymer compound is centered on absorption of 3.5 μm, and 0.78 μm to 20 μm is particularly preferable. These infrared rays can be spotted or linearly focused by a mirror or a lens, and a heater called a spot heater or a line heater that narrows the heating area of the original filament can be used. The line heater is suitable when a plurality of original filaments are traveling in parallel.

The infrared light beam of the present invention is particularly preferably laser light. Among these, a carbon dioxide laser with a wavelength of 10.6 μm and a YAG (yttrium, aluminum, garnet) laser with a wavelength of 1.06 μm are particularly preferable. Lasers can narrow the radiation range (light flux) to a small size, and are concentrated on a specific wavelength, so there is little wasted energy. The carbon dioxide laser of the present invention has a power density of 50 W / cm ² or more, preferably 100 W / cm ² or more, and most preferably 180 W / cm 2 or more. This is because the ultrahigh magnification stretching of the present invention can be achieved by concentrating energy of high power density in a narrow stretching region.

  The original filament of the present invention is heated to an appropriate stretching temperature by an infrared light beam irradiated by an infrared heating means (including a laser). In the present invention, the original filament is heated by the infrared light beam, but the range heated to an appropriate stretching temperature is preferably within 4 mm (up to 8 mm) in the vertical direction along the axial direction of the filament. Is heated up to 3 mm or less, most preferably up to 2 mm or less. The diameter of the luminous flux is measured along the axial direction of the traveling filament. When there are a plurality of original filaments, a slit-shaped light beam is also used. In this case, it is preferable that the narrowest portion coincides with the axial direction of the original filament. The present invention has been made extremely thin by abrupt stretching in a narrow region, enables stretching to a nano region, and can reduce stretching breakage even with ultra-high magnification stretching. .

The ES method, which is a conventional production method of nanofibers, requires the solvent to be removed from the work of dissolving the polymer in the solvent or the finished product, and is complicated and costly in the manufacturing method. In addition, the resulting product also had a problem in quality as a structure, such as a mass of resin called lumps or shots, and a wide distribution of filament diameters. The resulting fiber is also a short fiber and is said to be several millimeters to several tens of millimeters in length. However, in the present invention, a three-dimensional structure composed of substantially continuous filaments can be obtained.
The present invention does not require a special high-precision and high-level apparatus, and can obtain ultrafine filaments with improved molecular orientation easily by simple means, and a three-dimensional structure can be obtained by collecting and molding. .

Furthermore, the present invention provides a three-dimensional structure of ultrafine filaments from a filament made of a biodegradable polymer used as a regenerative medical material such as polylactic acid or polyglycolic acid, which has poor stretchability in normal stretching, to a nanofilament region. can get. The ES method, which is a conventional nanofiber manufacturing method, uses a solvent such as chloroform, so it not only needs to be dissolved and desolvated, but also uses such a harmful solvent, which Use in is difficult.
The three-dimensional nanofiber structure in the present invention not only dramatically improves the filter efficiency in the conventional air filter field, but also is utilized as a material that can be applied to a wide range of applications in the bio and environmental fields. In addition, the present invention can be easily converted into nanofibers from polyarylate-based polymers, polyethylene naphthalate, fluorine-based polymers, etc., which are conventionally difficult to be ultrafine due to a narrow range of spinning and stretching conditions, and is three-dimensional. A structure is obtained.

The outline of the apparatus for cotton-like nanofiber preparation is shown. A schematic view of a stainless steel cylindrical mold is shown. The photograph of the three-dimensional structure when it shape | molds by changing temperature and time is shown. The SEM photograph of the three-dimensional structure when it shape | molds by changing temperature and time is shown. The Trans / Gauche ratio obtained from FT-IR measurement of a three-dimensional structure is shown. (a) The compression recovery rate formed by changing the molding time and (b) the compression recovery rate changed by changing the bulk density. The SEM photograph of the three-dimensional structure formed by adding (a) NaCl and (b) the three-dimensional structure after washing and drying is shown.

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram showing the principle of collecting the ultrafine filament of the present invention in a cotton shape, and shows a sectional view of the apparatus. The original filament 1 is unwound from the state wound on the reel 2, sent out at a constant speed, and led to the orifice 3. In the steps so far, the original filament supply side is kept at the pressure P1.

  After the orifice 3 outlet, it becomes the stretching chamber 4 under P2 atmospheric pressure. The original filament 1 exiting the orifice 3 is guided to the drawing chamber 4 together with high-speed air caused by the pressure difference P1-P2 between the original filament supply side and the drawing chamber. The delivered original filament 1 is irradiated with a laser beam 6 from a laser oscillation device 5 to a heating region having a certain width from the laser oscillation device 5 immediately below the orifice. It is preferable that a laser beam power meter 7 is provided at the destination of the laser beam 6 and the laser power is adjusted to be constant. The original filament is drawn by the tension applied to the lower filament by the high-speed air heated by the laser beam 6 and brought about by the P1-P2 pressure difference, and descends as a drawn filament. 8 is accumulated as a cotton filament 11. The atmospheric pressure P2 is adjusted by a valve 10 or the like led to a vacuum pump (not shown). The stretching chamber 4 is also provided with a pressure gauge 9.

The apparatus for producing cotton-like nanofibers (Fig. 1) consists of a laser oscillator, fiber supply reel, fiber supply orifice, nanofiber collection container, vacuum chamber (stretching chamber) with Zn-Se window, and power meter. The In this apparatus, cotton-like nanofibers with various fiber diameters can be produced by changing the drawing conditions such as the fiber supply speed, laser output, laser irradiation position, and chamber pressure.
The sample used was a polyethylene terephthalate (PET) fiber obtained by melt spinning, and had a fiber diameter of 534 μm, a melting point of 256.7 ° C., and a crystallinity of 11.7%. This PET fiber is stretched under the conditions of a laser output of 30 w, a fiber supply rate of 0.1 m / min, a vacuum chamber pressure of 10 kPa, an orifice diameter of 0.3 mm, and a laser irradiation position of 20 mm, collected in a collection container, and bulky cotton. PET nanofibers were prepared. The average fiber diameter was 534 nm (maximum 750 nm-minimum 360 nm).
A stainless steel cylindrical mold (FIG. 2) was used as a mold for heat compression molding of nanofibers. The mold has a diameter of 1 cm, a height of 1 cm, and a volume of 0.785 cm ³ . In the formation of the three-dimensional structure, first, a predetermined amount of cotton-like nanofibers was packed in a mold, and heated using a press machine set at 270 ° C. for 1 minute to perform compression molding.
Fiber amount 51.5 mg (bulk density 0.0656 g / cm ³ ), 41.5 mg (0.0529 g / cm ³ ), 30.4 mg (0.0387 g / cm ³ ), 19.0 mg (0.0242 g / cm) ³ ). At 30.4 mg and 19.0 mg with a small amount of fiber, the amount of fiber was small, so that the entire structure contracted due to the thermal contraction of the nanofiber, and the shape of the mold could not be shaped.
Fig. 3 is a photograph of a three-dimensional structure that has been subjected to heat compression molding with a constant fiber amount of 51.5 mg, a heat compression molding temperature in the range of 150 ° C to 270 ° C, and a heat compression molding time of 1, 5, 10 minutes Indicates. Since the heating was insufficient at a molding temperature of 150 ° C. and a molding time of 1 minute and 5 minutes, molding was impossible. Further, when the molding temperature was 270 ° C. and the molding time was 5 minutes and 10 minutes, the thermal contraction of the PET nanofibers became remarkable and the shape could not be maintained. Moreover, each SEM photograph is shown in FIG. Fiber fusion was observed at a molding temperature of 270 ° C. and a molding time of 10 minutes.
FIG. 5 shows the Trans / Gauche ratio obtained from the FT-IR measurement of a three-dimensional structure formed by hot compression molding at a molding temperature ranging from 150 ° C. to 270 ° C. and changing the molding time to 1, 5, and 10 minutes. As the molding temperature increased, the Trans / Gauche ratio increased, suggesting that crystallinity increased. However, at 270 ° C., the Trans / Gauche ratio decreases, indicating that molecular chain orientation relaxation occurs due to thermal shrinkage caused by partial melting of the crystal. Fig. 6 shows (a) the compression recovery rate of a three-dimensional structure formed by changing the forming time to 1, 3, 5, and 10 minutes at a forming temperature of 250 ° C and (b) the forming temperature of 250 ° C by changing the bulk density. The compression recovery rate of the three-dimensional structure molded in 10 minutes is shown. The compression restoration rate was calculated from the compression restoration rate [%] = {(t ₀ −t ₁ ) / (t ₀ −t ₂ )} × 100.
Here, t ₀ is the thickness of the sample before compression, t ₁ is the thickness when compressed, t ₂ is the thickness of the sample after 24 hours left to release from compression. As the molding time increases, the restoration rate increases, and the increase in fiber strength accompanying the improvement in crystallinity contributes to the improvement in the restoration rate. Further, the restoration rate decreases as the bulk density of the three-dimensional structure increases. It is considered that as the bulk increases, the fibers are entangled with each other to inhibit the restoration. The restoration rate of the three-dimensional structure having a bulk density of 63.7 mg / cm ³ produced at a molding temperature of 250 ° C. and a molding time of 10 minutes was 98.1%, the highest.

When nanofibers are heat compression molded, if the amount of fibers packed in the mold is small, the nanofibers cannot be molded into the mold shape due to thermal shrinkage. Therefore, an excipient that can be removed after molding was added to mold a three-dimensional structure. Here, salt (NaCl) that can be removed by washing with water was used as an excipient. In order to perform heat compression molding using an excipient, first, NaCl fine particles pulverized to a particle size of 10 to 30 μm and a predetermined amount of nanofibers are uniformly mixed with a blender. The nanofibers to which NaCl is added are packed in a mold and heated by a press at 270 ° C. for 5 minutes for compression molding. After the molding, in order to remove NaCl, it was washed with warm water at 80 ° C. for 6 hours, washed with water and dried in a vacuum oven at 100 ° C. for 24 hours.
When a cylindrical PET-3D structure was molded by adding 446.3 mg of excipient (NaCl) to 31.7 mg of fiber, the bulk density was 0.040 g / cm ³ . The bulk density was 0.021 g / cm ³ when the fiber amount was 16.6 mg and the excipient (NaCl) 301.5 mg was added. By adding an excipient, a three-dimensional structure with a small bulk density can be produced, and three-dimensional structures with various bulk densities can be produced. FIG. 7 shows SEM photographs of (a) a three-dimensional structure formed by adding NaCl (fiber amount: 31.7 mg, containing NaCl) and (b) a three-dimensional structure after washing and drying. In the sample compression-molded with NaCl added (FIG. 7a), it is observed that nanofibers are uniformly dispersed in NaCl. In the three-dimensional structure after washing and drying, NaCl was almost completely removed, and the structure had three-dimensional pores (FIG. 7b).
Cotton-like nanofibers produced by a carbon dioxide laser supersonic stretching method can be formed into three-dimensional structures having various shapes other than a cylindrical shape. For example, it can be formed using a regular tetrahedron or sphere mold. When an acute angle part exists like a regular tetrahedron, when an excipient | filler is added, it can shape | mold according to a metal mold | die and a complicated-shaped three-dimensional structure can also be produced.

DESCRIPTION OF SYMBOLS 1 Original filament 2 Reel 3 Orifice 4 Stretch chamber 5 Laser oscillator 6 Laser light 7 Power meter 8 Collection container 9 Pressure gauge 10 Valve 11 Cotton filament 12 Mold lid part, bottom part 13 Mold cylinder part

Claims (3)

A three-dimensional structure manufactured by accumulating nanofilaments composed of one or a plurality of long fibers, collected in a cotton shape, and placing the cotton-like nanofilament in a mold and heat compression molding. A manufacturing method comprising:
In the heat compression molding by the mold, the excipient for molding into the shape as the mold is mixed with the nanofilament, then the heat compression molding,
A void is formed by removing the excipient from the heat compression molded product ,
In the nanofilament, the original filament delivered by the filament delivery means is supplied to the orifice under P1 atmospheric pressure, and the difference in atmospheric pressure before and after the orifice is led to the extending portion under P2 atmospheric pressure where P1 ≧ 2P2. A manufacturing method of a three-dimensional structure, wherein the three-dimensional structure is manufactured by being heated and stretched by an infrared light beam in the extending portion .   The method for producing a three-dimensional structure according to claim 1, wherein the excipient is sodium chloride.   A three-dimensional structure manufactured by the three-dimensional structure manufacturing method according to claim 1.