Method of manufacturing high strength synthetic fibers
Provided is a method of manufacturing high strength synthetic fibers, and high strength synthetic fibers manufactured using the same. More particularly, the method involves a localized heating process by raising the temperature of a molten spinning fiber to a temperature higher than that of a pack body during a short period of time with no degradation through a heating zone located in the immediate vicinity of capillary in the spinning nozzle, so as to effectively control the molecular entanglement structure in the molten polymer without reducing the molecular weight and thus to enhance the drawability of the as-spun fibers, thereby improving the mechanical properties of the as-spun fibers, such as strength, elongation, etc., using the existing processes of melt spinning and drawing and thus enabling a mass production of a high-performance fiber at low cost.
1. A method of manufacturing high strength synthetic fiber, comprising:
melt-spinning a thermoplastic polymer through a spinning nozzle containing at least one capillary to form molten fiber;
passing the molten fiber through a heating zone ( 40 or 80 ) located in the immediate vicinity of the spinning nozzle ( 12 or 52 ) to heat the fiber;
cooling down the heated fiber; and
drawing the cooled fiber and then winding the drawn fiber,
wherein the molten fiber is locally heated by passing through the heating zone ( 40 or 80 ) including a high-temperature heater ( 41 or 81 ) provided in the form of a hole-type heating channel ( 41 a or 81 a ) or a band-type heating channel ( 41 b or 81 b ) formed on the periphery of the capillary of the spinning nozzle,
wherein the molten fiber passes through a high-temperature heater ( 41 or 81 ) provided in the form of a plurality of a hole-type heating channel ( 41 a or 81 a ) having apart from the center of each capillary of the spinning nozzle at a distance of 1 to 300 mm.
2. The method as claimed in claim 1 , wherein the thermoplastic polymer comprises any one selected from a polyester-based polymer selected from the group consisting of polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polycyclohexane dimethanol terephthalate (PCT), and polyethylene naphthalate (PEN); a polyamide-based polymer selected from the group consisting of nylon 6, nylon 6,6, nylon 4, and nylon 4,6; or a polyolefin-based polymer selected from the group consisting of polyethylene and polypropylene.
3. The method as claimed in claim 1 , wherein the molten fiber is locally heated up to high temperature instantaneously when passing through the high-temperature heater ( 41 or 81 ) having a temperature difference of 0 to 1,500° C. from a pack body ( 20 or 60 ).
4. The method as claimed in claim 3 , wherein the pack body ( 20 or 60 ) is maintained at temperature of 50 to 400° C.
5. The method as claimed in claim 1 , wherein the fiber passes through a high-temperature heater ( 41 or 81 ) provided in the form of a plurality of a band-type heating channel ( 41 b or 81 b ) formed in an arrangement disposed between adjacent capillaries, when the plurality of the capillary are arranged in a same radius from the center of the spinning nozzle.
6. The method as claimed in claim 1 , wherein the heating zone ( 40 ) is defined to include an insulator ( 43 ) having a thickness of 1 to 30 mm below the bottom of the spinning nozzle and a high-temperature heater ( 41 ) extending to a length of 1 to 500 mm from the insulator.
7. The method as claimed in claim 1 , wherein the heating zone ( 80 ) is defined to include a high-temperature heater ( 81 ) is in contact with or partly inserted into the bottom of a spinning nozzle ( 52 ), the bottom of the spinning nozzle ( 52 ) being positioned at a distance of −50 mm (inside the pack body) to 300 mm (outside the pack body) from the bottom of a pack body, wherein the high-temperature heater ( 81 ) is inserted into the bottom of the spinning nozzle ( 52 ) to an insertion length of 0 to 50 mm and extends from the bottom of the spinning nozzle to an extension length of 0 to 500 mm.
8. The method as claimed in claim 1 , wherein the thermoplastic polymer passing through each capillary ( 11 or 51 ) of the spinning nozzle ( 12 or 52 ) has a residence time of 3 seconds or less and a throughput rate of at least 0.01 cc/min.
9. The method as claimed in claim 1 , wherein the shear rate on the wall surface of a capillary in the spinning nozzle ( 12 or 52 ) is 500 to 500,000/sec.
10. The method as claimed in claim 1 , wherein the capillary ( 11 or 51 ) of the spinning nozzle ( 12 or 52 ) has a structure with a diameter (D) of 0.01 to 5 mm, a length (L), wherein L/D is 1 or greater, a pitch (the distance of the adjacent two capillaries) of 1 mm or greater, and a cross-section taking a circular shape or a noncircular shape.
11. The method as claimed in claim 1 , wherein the spinning nozzle ( 12 or 52 ) is a nozzle for at least one single or multicomponent spinning method selected from the group consisting of sheath-core type, side-by-side type, and islands in the sea type.