Method of manufacturing high-strength sheath-core type synthetic fiber, and high-strength sheath-core type synthetic fiber manufactured thereby

Abstract

The present disclosure relates to a method of manufacturing a high-strength sheath-core type synthetic fiber and high-strength sheath-core type synthetic fiber manufactured thereby, the method including forming a fiber by melt-spinning a thermoplastic polymer of a sheath component and a core component through a spinning pack including a sheath-core type bicomponent spinning nozzle; performing a heat treatment by allowing a molten fiber to pass through a heating zone disposed directly below the spinning nozzle during the melt-spinning; cooling the heat-treated fiber; and drawing the cooled fiber, wherein the sheath component includes a resin including the sheath component having elongation viscosity and thermal conductivity lower and specific heat higher than those of a resin included in the core component, and an ultra-fine high-strength synthetic fiber satisfying predetermined strength or higher as compared to a fine diameter and intrinsic viscosity may be provided.

1 . A method of manufacturing a high-strength sheath-core type synthetic fiber, the method comprising:
 forming a fiber by melt-spinning a thermoplastic polymer of a sheath component and a core component, through a spinning pack including a sheath-core type bicomponent spinning nozzle;   performing a high-temperature heat treatment by allowing a molten fiber to pass through a heating zone disposed directly below the spinning nozzle during the melt-spinning;   cooling the heat-treated as-spun fiber; and   drawing the cooled as-spun fiber,   wherein the sheath component includes a resin including the sheath component having elongation viscosity and thermal conductivity lower and specific heat higher than those of a resin included in the core component.   
     
     
         2 . The method of  claim 1 , wherein the sheath-core type synthetic fiber includes an islands-in-the-sea type fiber. 
     
     
         3 . The method of  claim 1 , wherein, when the sheath-core type synthetic fiber is an islands-in-the-sea type fiber, a volume ratio between a sea component and an island component is 10:90 to 90:10. 
     
     
         4 . The method of  claim 1 , wherein a thermoplastic polymer of the sheath component and the core component is independently selected from a group consisting of at least one polyester-based polymer selected from a group consisting of polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polycyclohexanedimethanol terephthalate (PCT), polylactic acid (PLA), polyethylene naphthalate (PEN), polyethylene furanoate (PEF), and polyarylate (PAR); at least one polyamide-based polymer selected from among nylon 6, nylon 6,6, nylon 4 and nylon 4,6; and at least one polyolefin-based polymer selected from a group consisting of polyethylene and polypropylene. 
     
     
         5 . The method of  claim 1 , wherein a difference in thermal conductivities of thermoplastic polymers between the sheath component and the core component is 0.01 J/m·s·K to 10 J/m·s·K, and a difference in specific heats therebetween is 0.05 KJ/Kg·K to 50 KJ/Kg·K. 
     
     
         6 . The method of  claim 1 , wherein thermoplastic polymers of the sheath component and the core component satisfy at least one of conditions as below: melt viscosity of 10 poise to 10,000 poise, glass transition temperature (Tg) of 5° C. to 300° C., and crystallinity temperature of 5° C. to 300° C. 
     
     
         7 . The method of  claim 2 , wherein the number of island fibers in the islands-in-the-sea type fiber is in a range of 1 to 1,000,000. 
     
     
         8 . The method of  claim 1 , wherein the heating zone locally heats the fiber by a heating element formed as a circular-type element or a strip-type element in a periphery of the spinning nozzle hole. 
     
     
         9 . The method of  claim 1 , wherein a residence time of the molten thermoplastic polymer passing through each hole in the spinning nozzle is 3 seconds or less, and a flow rate is 0.01 cc/min to 10 cc/min. 
     
     
         10 . A sheath-core type synthetic fiber formed of a sheath component and a core component, wherein the sheath component includes a resin having elongation viscosity and thermal conductivity lower and specific heat higher than those of a resin included in the core component. 
     
     
         11 . The sheath-core type synthetic fiber of  claim 10 , wherein a difference in thermal conductivities of thermoplastic polymers between the sheath component and the core component is 0.01 J/m·s·K to 10 J/m·s·K, and a difference in specific heats therebetween is 0.05 KJ/Kg·K to 50 KJ/Kg·K. 
     
     
         12 . The sheath-core type synthetic fiber of  claim 10 , wherein thermoplastic polymers of the sheath component and the core component satisfy at least one of conditions as below: melt viscosity of 10 poise to 10,000 poise, glass transition temperature (Tg) of 5° C. to 300° C., and crystallinity temperature of 5° C. to 300° C. 
     
     
         13 . The sheath-core type synthetic fiber of  claim 10 , wherein the sheath-core type fiber is an islands-in-the-sea type fiber containing polyethylene terephthalate (PET) island yarn including an island component having a diameter of 10 nm to 500 μm and satisfying physical properties equal to or higher than strength calculated by Equation 1 below:
   Strength (tensile strength, g/d)=15.873×intrinsic viscosity (I.V.) of PET fiber−3.841  Equation 1.
 
 
     
     
         14 . The sheath-core type synthetic fiber of  claim 13 , wherein the island yarn has an intrinsic viscosity (I.V.) of 0.5 to 3.0. 
     
     
         15 . The sheath-core type synthetic fiber of  claim 10 , wherein the sheath-core type fiber is an islands-in-the-sea type fiber including an island component having a diameter of 10 nm to 500 μm and containing nylon island yarn satisfying physical properties equal to or higher than strength calculated by Equation 2 below: 
       
         
           
             
               
                 
                   
                     
                       Strength 
                       ⁢ 
                          
                       
                         ( 
                         
                           
                             tensile 
                             ⁢ 
                                 
                             strength 
                           
                           , 
                           
                             g 
                             / 
                             d 
                           
                         
                         ) 
                       
                     
                     = 
                     
                       
                         8.6 
                         × 
                         relative 
                         ⁢ 
                             
                         viscosity 
                         ⁢ 
                            
                         
                           ( 
                           
                             R 
                             ⁢ 
                             v 
                           
                           ) 
                         
                         ⁢ 
                            
                         of 
                         ⁢ 
                             
                         nylon 
                         ⁢ 
                             
                         fiber 
                       
                       - 
                       14.44 
                     
                   
                 
                 
                   
                     Equation 
                     ⁢ 
                         
                     2 
                   
                 
               
             
           
         
       
     
     
         16 . The sheath-core type synthetic fiber of  claim 15 , wherein the island yarn has a relative viscosity (Rv) of 2.0 to 5.0. 
     
     
         17 . The sheath-core type synthetic fiber of  claim 10 , wherein, when two or more melting point peaks are present on a DSC of the core component, a difference in temperatures therebetween peaks is 10° C. or less.