Abstract
The present invention relates to means for manufacturing micro-beads (polymer micro-particles) comprising thermoplastic polymer and having the average particle size of 10 μm or less, and extending into the nano-range. An original filament comprising a thermoplastic polymer is passed through an orifice under an air pressure (P1) and guided to a spray chamber under a pressure (P2; where P1>P2). The original filament having passed through the orifice is heated and melted under irradiation by an infrared beam, and is sprayed in microparticulate form from the orifice by the flow of air generated by the pressure differential between P1 to P2, whereby micro-beads comprising thermoplastic polymer micro-particles having an average particle size of 10 μm or less, and even less than 1 μm are manufactured.
Claims
1. A method of manufacturing micro-beads comprising thermoplastic micro-particles with an average particle size of 10 μm or smaller, the method comprising: transferring an original filament comprising a thermoplastic polymer under a pressure P1 through an orifice and into a spray chamber under a pressure P2, wherein P1>P2; irradiating the original filament that passed through the orifice in the spray chamber using an infrared beam; and spraying the melted filament into microparticles using a gas flow generated by the pressure differential between P1 and P2, wherein the micro-beads have an average particle size of less than 1 μm.
2. The method according to claim 1, wherein the original filament is heat treated while the original filament is introduced into the orifice.
3. A method of manufacturing micro-beads comprising thermoplastic micro-particles with an average particle size of 10 μm or smaller, the method comprising: transferring an original filament comprising a thermoplastic polymer under a pressure P1 through an orifice and into a spray chamber under a pressure P2, wherein P1>P2; irradiating the original filament that passed through the orifice in the spray chamber using an infrared beam; and spraying the melted filament into microparticles using a gas flow generated by the pressure differential between P1 and P2, wherein the original filament has a degree of crystallization of at least 25% according to differential scanning calorimetric (DSC) measurements.
4. The method according to claim 1, wherein the microparticles and the drawn filament obtained as a byproduct along with the microparticles are accumulated on a filter inside a vacuum chamber.
5. The method according to claim 4, wherein the filter forms a conveyer that circulates the filter.
6. A method of manufacturing micro-beads comprising thermoplastic micro-particles with an average particle size of 10 μm or smaller, the method comprising: transferring an original filament comprising a thermoplastic polymer under a pressure P1 through an orifice and into a spray chamber under a pressure P2, wherein P1>P2; irradiating the original filament that passed through the orifice in the spray chamber using an infrared beam; and spraying the melted filament into microparticles using a gas flow generated by the pressure differential between P1 and P2, wherein P1 is atmospheric pressure and P2 is reduced pressure.
7. The method to claim 1, wherein the infrared beam is a carbon dioxide laser beam.
8. The method according to claim 1, wherein the center of the infrared beam irradiates the original filament within 30 mm of the orifice exit.
9. The method according to claim 1, wherein the infrared beam irradiates the original filament center within 4 mm along a filament axis direction.
10. The method according to claim 1, comprising subjecting the micro-beads to a heat treatment at a temperature at or above a softening point of the micro-beads and yet at or below a melting point of the thermoplastic polymer.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) FIG. 1 The figure is a conceptual diagram of a device that describes the principle of producing micro-beads comprising thermoplastic micro-particles of the present invention.
(2) FIG. 2 The figure is a conceptual diagram showing an example wherein micro-beads manufacturing means of the present invention contain a filter.
(3) FIG. 3 The figure is a conceptual diagram showing an example wherein micro-beads manufacturing means of the present invention contain a scraper for collection.
(4) FIG. 4 The figure is a conceptual diagram showing an example wherein micro-beads manufacturing means of the present invention contain a conveyer comprising a filter.
(5) FIG. 5 The figure is a conceptual diagram showing an example of the orifice in the present invention.
(6) FIG. 6 The figure is a conceptual diagram showing another example of the orifice in the present invention.
(7) FIG. 7 The figure is a conceptual diagram showing an example in which an original filament is irradiated at multiple locations using mirrors to reflect an infrared beam in the present invention.
(8) FIG. 8 The figure is a conceptual diagram showing an example in which multiple infrared beam radiating devices are positioned to irradiate an original filament from multiple locations in the present invention.
(9) FIG. 9 The figure is an electron microscope photograph (magnification 5,000) of poly(ethylene terephthalate) micro-beads formed according to the present invention.
(10) FIG. 10 The figure is a histogram showing the particle size distribution of poly(ethylene terephthalate) micro-beads formed according to the present invention.
(11) FIG. 11 The figure is an electron microscope photograph (magnification 1,000) of poly(L-lactic acid) (PLLA) micro-beads formed according to the present invention.
(12) FIG. 12 The figure is an electron microscope photograph (magnification 10,000) of high density polyethylene micro-beads formed according to the present invention.
(13) FIG. 13 The figure is an electron microscope photograph (magnification 30,000) of PFA (tetrafluoroethylene perfluoroalkyl vinyl ether) copolymer micro-beads formed according to the present invention.
EMBODIMENT OF THE INVENTION
(14) Examples of the embodiment of the present invention are described below based on the figures. FIG. 1 shows an example of a conceptual diagram of the manufacturing principle for ultrafine filaments comprising thermoplastic polymer according to the present invention, and a perspective view of a device is shown. An original filament 1 comprising thermoplastic polymer is released from a reel 2 on which it is wound and is rolled out at a constant speed using roll out nip rollers (not shown in FIG. 1). Although the roll out nip rollers is omitted from the figure, the roll out rollers may be substituted by rotating the reel 2 at a constant rotary speed. The rolled out original filament 1 is led to an orifice 3. The entire original filament from the reel 2 to the orifice 3 remains in an original filament supply chamber 4, and the pressure is maintained at P1. The pressure P1 is maintained at a constant level using a valve 5 and a pressurizing pump (not shown in FIG. 1). The section after the orifice 3 exit is a spray chamber 6 under P2 pressure (a negative pressure in FIG. 1). The pressure P2 is maintained at a constant level using a valve 7 and a vacuum pump (not shown in FIG. 1). The original filament exiting from the orifice 3 is led into a spray chamber 6 along with the high speed air flow generated by the pressure differential between the original filament supply chamber 4 and the spray chamber 6. The original filament 1 is irradiated immediately below the orifice 3 using a laser beam 9 released by a carbon dioxide gas laser oscillation device 8. Now, in order to guide a laser beam 9 into the spray chamber 6, the laser beam must pass through a Zn—Se window 10a. Now, the laser beam 9 exits the Zn—Se window 10b that corresponds to a section of the spray chamber 6 wall and reaches a power meter 11. The original filament that has been heated and melted by the laser beam 9 is sprayed in the form of mist using the high speed air generated by the pressure difference between P1 and P2 and descends in the form of a sprayed micro-particle group 12. Micro-particles accumulation chamber 13 are a space under P2 pressure connected to the spray chamber 6 and is located on the bottom of the spray chamber 6. A micro-particle collection vessel 14 is present inside the micro-particle accumulation chamber 13, and the sprayed micro-particles 12 are collected in the collection vessel 14. The degrees of pressurization and vacuum are adjusted using valves 5 and 7 and a bypass valve and the like.
(15) FIG. 2 shows an example of a conceptual diagram of the micro-beads manufacturing means of the present invention containing a filter. The original filament 22 wound on a reel 21 is rolled out and is led into a spray chamber 23 under P2 pressure that is a negative pressure through an orifice 24. The original filament 22 that passed through the orifice 24 is heated using an infrared beam 25 and is sprayed using the gas flow passing through the orifice 24 to form micro-particles 26. The micro-particles 26 are guided into a collection vessel 27. A filter 28 is installed on the bottom of the collection vessel 27, and the negative pressure inside the spray chamber 23 is maintained constant using a vacuum pump (not shown in FIG. 2) through a valve 29 in a pipe connecting to the filter 28.
(16) FIG. 3 shows an example of a conceptual diagram of a micro-beads manufacturing apparatus with a scraper for collection. The original filament 32 discharged from the orifice 31 becomes sprayed micro-particles 34 using the gas flow from an orifice 31 and the heat from an infrared beam 33. The micro-particles 34 are sometimes accompanied by the drawn filaments produced as a byproduct. The sprayed micro-particles accumulate on a conveyer 35 circulating inside a spray chamber (not shown in FIG. 3 but is positioned below the orifice 31). A scraper 36 is used to remove the micro-particles and collect them inside a collection vessel 37.
(17) FIG. 4 shows the conceptual diagram of a micro-beads manufacturing apparatus with a conveyer comprising a filter and show its perspective view. The original filaments 41a, 41b, 41c, . . . comprising thermoplastic polymer are rolled out from a reel 42 and are transferred at a constant speed through a comb and the like (not shown in the figure) using roll out nip rollers (not shown in FIG. 4) and the like. Multiple orifices 44a, 44b, 44c, . . . are carved (or drilled) in a plate 43, and the original filament 41 comprising a thermoplastic polymer transferred is led to the orifice 44. The steps up to this point in the figure are shown in the figure to illustrate a case in which the pressure P1 in an original filament supply chamber is maintained at atmospheric pressure and no special chamber is needed. The area after the exit from the orifices 44a, 44b, 44c, . . . becomes a spray chamber 45 under pressure P2 (negative pressure in this figure shown). The pressure P2 is maintained at a constant level using a valve 46 from a vacuum pump (not shown in FIG. 4). The original filaments 41a, 41b, 41c, . . . exiting from the orifices 44a, 44b, 44c, . . . are led to a spray chamber 45 along with the high speed air generated by the pressure difference between the original filament supply chamber and the spray chamber. A laser beam 48 discharged (or emitted) from a carbon dioxide gas laser oscillation device 47 irradiates multiple original filaments 41 directly under the orifice 44. Now, the laser beam 48 passes through a window 49 comprising Zn—Se in order to guide the beam into the spray chamber 45. The original filament 41 is heated and melted by the laser beam 49, sprayed using the high speed air generated by the pressure difference between P1 and P2 and descends in the form of a sprayed material 50a, 50b, 50c, . . . comprising micro-particles grouping and drawn filaments formed as a byproduct. A conveyer 51 comprising a filter is circulating in the lower section of the spray chamber 45, and the sprayed material 50 accumulates on the conveyer 51. A vibrator 52 is installed on the conveyer 51, and the vibrator 52 functions to allow the micro-particle grouping 54 to fall off from the sprayed material 50 on the conveyer 51 made of a filter leaving a web 53 comprising the drawn filaments to remain on the conveyer 51. The micro-particle grouping 54 that fell off is received by a sloped collection plate 55 and accumulates inside a collection box 56 after falling along the slope. In order to smoothly transfer the micro-particle grouping 54 from the collection plate 55 to the collection box 56, the installation of a vibrator 57 also on the collection plate is desirable. In addition, the micro-particle grouping 54 on the collection plate 55 may also be heat treated using an infrared heating and the like. Now the web 53 on the conveyer 31 is rolled up by a web rolling device (not shown in FIG. 4) and is continuously removed from the conveyer 51.
(18) FIG. 5 shows a cross sectional diagram of an orifice that is an example of one orifice mode in the present invention. FIG. 5 shows a simple cylindrical orifice 62 through which an original filament 61 with the filament diameter (d) passes through. The internal orifice diameter in the exit section is D1. The original filament 61 exiting the orifice 62 is irradiated with an infrared light beam 63. Then the orifice exit is positioned to minimize the distance (L) to the infrared light beam 63 center as much as possible.
(19) FIG. 6 shows an orifice cross sectional diagram of another orifice mode. Figure (a) shows one type of orifice 64 with a large entrance section and a thinner exit section with the internal diameter (D2). Figure (b) is a conceptual diagram showing a partial cross section of an orifice 65 through which multiple filaments are simultaneously discharged. The exit diameter (D3) in Figure (b) is shown using the narrowest direction and the diameter in the thickness direction.
(20) FIG. 7 shows an example of a means used to irradiate an original filament from multiple locations using an infrared light beam in the present invention. Figure A is a front view and Figure B is a side view. The infrared light beam 71a emitted from an infrared light beam irradiation device reaches a mirror 73 after passing a zone P (inside the dotted line in FIG. 7) through which an original filament 72 passes to become an infrared light beam 71b reflected by the mirror 73. The light beam becomes an infrared light beam 71c upon reflection on a mirror 74. The infrared light beam 71c moves through the zone (P) and irradiates the original filament 72 at one hundred twenty degrees later from the initial original filament irradiation position. The infrared light beam 71c that passes through the zone (P) is reflected by a mirror 75 to become an infrared light beam 71d and is reflected by a mirror 76 to become an infrared light beam 71e. The infrared light beam 71e passes through the zone (P) and irradiates the original filament 72 at an opposite one hundred twenty degrees later from the infrared light beam 71c in the initial original filament irradiation location. The original filament 72 can be heated evenly from symmetrical one hundred twenty degrees away from each other using three infrared light beams 71a, 71c, 71e in the manner described.
(21) FIG. 8 shows another example of the original filament irradiation means wherein the original filament is irradiated from multiple locations using infrared light beams used in the present invention, and an example in which multiple light source is used is shown using a front view. The infrared light beam 77a emitted from an infrared irradiation device is used to irradiate an original filament 72. In addition, the original filament 72 is also irradiated with an infrared light beam 77b emitted from a different infrared irradiation device. Furthermore, the original filament 75 is irradiated using an infrared light beam 77c irradiated from yet another infrared irradiation device. In the manner described, radiation from multiple light sources can provide a high power light source by using multiple stable and inexpensive laser emitting devices as a high powered light source. Now three light sources are shown in the figure, but two may also be used and four or more may also be used. A multifilament comprising multiple original filaments is sprayed effectively using such multiple light sources.
Example 1
(22) An undrawn (or as-spun) polyethylene terephthalate (PET) filament (filament diameter: 110 μm, a degree of crystallinity: 7%) was used as the original filament, and a degree of crystallinity became 41% after a ten minute heat treatment at 260° C. The heat treated PET original filament was used, and micro-beads spraying were conducted using the spraying device in FIG. 1. The annealed filament was heated by the laser irradiation at a laser output power of 20 W, and its beam diameter (light beam) was 1.8 mm. The orifice shown in FIG. 6(a) was used as the orifice, and the orifice diameter (d2) was 0.5 mm. The degree of vacuum (or chamber pressure) in the spray chamber was adjusted so that (P1) was atmospheric pressure and (P2) was 16 kPa. When the original filament was supplied at a rate of 0.1 m/min, micro-beads with even particle size and high sphericity shown in the FIG. 9 SEM photograph (magnification 5,000) were formed. The particle size distribution at this point concentrated in the area of from 0.8 μm to 1.2 μm as shown in FIG. 10, and a narrow distribution width was observed. The average particle size was 0.9 μm at this point and qualified as nano particles. Now, micro-beads were little or not obtained and nano filaments were obtained when the original filament prior to the heat treatment with a degree of crystallization of 7% was used without additional treatments.
Example 2
(23) A poly-L-lactic acid (PLLA) drawn filament (filament diameter 75 μm) was used as the original filament, and a degree of crystallinity became 60% after a 10 minute heat treatment at 160° C. The heat treated PLLA original filament was used, and micro-beads spraying were conducted using the spraying device in FIG. 4. The annealed filament was heated by the laser irradiation at a laser output power of 20 W, and its beam diameter was 1.8 mm. The orifice shown in FIG. 6(a) was used as the orifice, and the orifice diameter (d2) was 0.5 mm. The degree of vacuum (or the chamber pressure) in the spray chamber was adjusted so that (P1) was atmospheric pressure and (P2) was 16 kPa. When the original filament was supplied at a rate of 0.1 m/min, micro-beads with only a slight amount of drawn filament in the FIG. 11 SEM photograph (magnification 1,000) were formed. The drawn filament was filtered using a 30 mesh filter, and the average particle size of the micro-beads upon filtration was 0.76 μm.
Example 3
(24) A high density polyethylene (MFR:1.0, a degree of crystallinity: 60%) drawn filament (filament diameter:176 μm) was used as the original filament, and the drawing (spraying?) device shown in FIG. 1 was used to spray micro-beads. The filament was heated by the laser irradiation at a laser output power of 20 W, and the beam diameter was 1.8 mm. The orifice shown in FIG. 6(a) was used as the orifice, and the orifice diameter (d2) was 0.5 mm. The degree of vacuum in the spray chamber was adjusted so that (P1) was atmospheric pressure and (P2) was 16 kPa. When the original filament was supplied at a rate of 0.1 m/min, micro-beads with high sphericity and even particle size shown in the FIG. 12 SEM photograph (magnification 10,000) were formed.
Example 4
(25) An undrawn tetrafluoroethylene•perfluoroalkyl vinyl ether copolymer (PFA) filament (filament diameter: 100 μm, a degree of crystallinity: 27%) was used as the original filament, and the spraying device shown in FIG. 1 was used to spray micro-beads. The degree of vacuum in the spraying chamber was adjusted to atmospheric pressure (P1) and (P2) 94 kPa. When the original filament was supplied at a rate of 0.1 m/min, micro-beads with high sphericity and even particle size shown in the FIG. 13 SEM photograph (magnification 30,000) were formed. The average particle size at this point was 50 nm, and the particles classified as nano particles.
INDUSTRIAL APPLICABILITY
(26) Polymer micro-particles have been used in the recent years to modify polymers, as additives to cosmetic and pharmaceutical products, as rheology modification agents for paint and the like since the particle size was small, the surface area was very large and they dispersed well in other substances. They particularly attracted attention as resin molding technology starting materials in rapid prototyping and the like where they were combined with laser processing technology to manufacture custom made molded products.
DESCRIPTION OF THE SYMBOLS
(27) 1: Original filament comprising thermoplastic polymer. 2: Reel. 3: Orifice. 4: Original filament supply chamber. 5: Valve. 6: Spray chamber. 7: Valve. 8: Carbon dioxide gas laser oscillation device. 9: Laser beam. 10a, 10b: Zn—Se windows. 11: Power meter. 12: Micro-particles grouping. 13: Micro-particles accumulation chamber. 14: Collection vessel. 21: Reel. 22: Original filament. 23: Spraying chamber. 24: Orifice. 25: Infrared beam. 26: Micro-particles 27: Collection vessel. 28: Filter. 29: Valve. 31: Orifice. 32: Original filament. 33: Infrared beam. 34: Micro-particles. 35: Conveyer. 36: Scraper. 37: Collection vessel. 41a, 41b, 41c: Original filament. 42: Reel. 43: Plate. 44a, 44b, 44c . . . : Orifice. 45: Spraying chamber. 46: Valve. 47: Carbon dioxide gas laser oscillation device. 48: Laser beam. 49: Zn—Se window. 50a, 50b, 50c . . . : Sprayed material. 51: Conveyer. 52: Vibrator. 53: Web. 54: Micro-particle grouping. 55: Collection plate. 56: Collection box. 57: Vibrator. 61: Original filament. 62: Orifice. 63: Infrared light beam. 64, 65: Orifice. 71a, 71b, 71c . . . : Infrared light beam. 72: Original filament. 73, 74, 75, 76: Mirrors. 77a, 77b, 77c . . . : Infrared light beam.
