Abstract:
Fibers of square cross sections are presented in the invention. The square fiber leads to higher packing density and results in higher wind resistance in fabrics as compared to the conventional round fibers and other polygonal fibers. Therefore, the square fiber is more suitable for manufacture of the windproof clothing. In addition, the square fibers exhibit higher luster than the round fibers and other polygonal fibers due to the flat and shiny fiber surface.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a Continuation-In-Part of application Ser. No. 10/282,083, filed Oct. 29, 2002, which claims the benefit of Taiwanese Application No. 90126697, filed Oct. 29, 2001. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a method of fabricating non-hollow fibers having regular polygonal cross-sections. In particular, the present invention relates to a method of fabricating a non-hollow fibers having a square cross-section with approximately equilateral sides. The present invention also relates to fabrics manufactured by the fibers, which demonstrate superior brightness, and windproof characteristics.  
         [0004]     2. Description of the Related Art  
         [0005]     Many efforts have been made to improve the characteristics of synthetic filaments or fibers so as to impart fabrics or textiles with enhanced performance and functions, such as moisture transport, thermal insulation, air permeability, antistatic, sustained release, antibacterial, and windproof properties.  
         [0006]     U.S. Pat. No. 5,057,368 issued to Largman et al, disclosed trilobal or quardrilobal filaments for use in various applications such as filtration, insulation, moisture transport and others.  
         [0007]     U.S. Pat. No. 5,279,879 issued to Goodall et al, disclosed a hollow synthetic filament having a four sided cross-section and four substantially evenly spaced continuous holes. The filament is suitable for making thermal wear and carpets which require extra thermal insulation or bulkiness.  
         [0008]     High density fabrics in which yarns are woven in a compact manner are more desirable for windproof wears. Such clothes are conventionally made of ultra-fine round filaments to reduce interfiber spaces and to achieve high fabric density. The present invention discovers that fibers of square cross section lead to even less interfiber spaces as compared to the conventional fine round filaments.  
       SUMMARY OF THE INVENTION  
       [0009]     The primary objective of the present invention is therefore to provide fabrics or textiles that demonstrate superior windproof (i.e., lower air permeability) characteristics and can be made at a lower cost.  
         [0010]     To attain the objective, the invention provides non-hollow fibers having square cross-section where each side has approximately equal length. The square fibers can be arranged in a denser manner, which has reduced interfiber spaces, when woven and finished properly. Therefore, the resultant fabrics or clothes possess superior windproof characteristics.  
         [0011]     Another advantage of this invention is that the dense fabrics made of the square fiber may impart superior thermal insulation due to reduction of air flow and thus heat loss by convection.  
         [0012]     A third unique attribute of this invention is that the fabrics made of the square fibers are more lustrous than conventional fabrics due to the flatter surface, which in turn is the result of the flat surface of the square cross section. The superior luster of the fabrics renders the designer an additional dimension in fashion design.  
         [0013]     The fibers or filaments of the present invention are made by using a spinneret orifice having a contoured quasi-polygonal cross-section.  
         [0014]     Specifically, the fibers or filaments of the invention are made by melting a thermoplastic polymer; extruding the melted polymer through a spinneret orifice having a contoured quasi-square cross-section to form molten filaments; and solidifying the molten filaments. The solidified filaments are subsequently drawn to achieve desired properties. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     The present invention can be more fully understood by reading the subsequent detailed description in conjunction with the examples and references made to the accompanying drawing, wherein:  
         [0016]      FIG. 1  is a photo showing the cross-section of the square fibers made in Example 1.  
         [0017]      FIG. 2  is a photo showing the cross-section of the triangular fibers made in Example 3. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]     The fibers or filaments of the invention are non-hollow fibers and filaments having square cross-section.  
         [0019]     The term “square” indicates that each side of the tetrahedral polygon has approximately equal length. It is noted, however, each side of square may have a variation less than 50%, preferably less than 5%, from the mean value  
         [0020]     The filaments are prepared by spinning molten polymer through spinneret capillaries or orifices designed to provide the desired configuration of the cross-section of the filaments. That is, the orifices are designed and formed in a configuration having a corresponding contoured polygonal cross-section.  
         [0021]     The filaments may be prepared from synthetic thermoplastic polymers. Examples of these polymers include but are not limited to polyester, polyamide and polyolefin.  
         [0022]     Polyesters that are suitable for use in this invention are those derived from the condensation of aromatic and cycloaliphatic dicarboxylic acids and may be cycloaliphatic, aliphatic or aromatic polyesters. Examples or these polyesters are poly(ethylene terephthalate), poly(proylene terephthalate), poly(cyclohexylenedimethylene terephthalate), poly(lactide), poly(butylene terephthalate), poly(glycolic acid) and poly(ethylene adipate). Among these, poly(ethylene terephthalate) is most frequently used. Other examples of suitable polyesters are those mentioned in U.S. Pat. Nos. 4,454,196, 4,410,073 and 4,359,557 incorporated herein for references.  
         [0023]     Polyamides of the above description are well known in this art and include, for example nylon  6  (poly(6-aminohexanoic acid)), nylon  66  (poly(hexamethyleneadipamide)), nylon  4  (poly(4-aminobutyric acid)), nylon  11  (poly(11-amino-undecanoic acid) and the like. The preferred polyamides are nylon  6  and nylon  66 . Other examples of suitable polyamides can be seen from “ Textile Fiber Handbook ”, 5th edition, Trowbridge GB (1984), pp 19-20.  
         [0024]     Examples of polyolefin that can be used in this invention as raw material include, but are not limited to polyethylene, polypropylene, polyisobutene, poly(4-methyl-1-pentene), poly(3-methyl-1-butene), and poly(1-hexene). Among these polyolefins, polypropylene is the most commonly used. Other examples of useful polyolefins can be found from U.S. Pat. Nos. 4,137,391, 4,562,869, 4,567,092 and 4,559,862 included herein for reference. Also, a blend of the above-mentioned polymers is also suitable for use according to the present invention.  
         [0025]     The manufacturing method of the fibers or filaments of the invention are substantially the same as conventional melt spinning techniques except that a spinneret orifice having a configuration sufficient to provide a fiber having regular polygonal cross-section is used. The raw material, i.e., the thermoplastic polymer, is melted and is extruded through the spinneret to form molten filaments. The spinning temperature is usually set between 150-300° C., depending on the melting point of the polymer and the type of the spinneret. For example, if polyethylene terephthalate is used as raw material, it is heated to 270-300° C. to melt the polymer. However, if polypropylene is employed, the spinning temperature is preferably set in the range of 200-280° C.  
         [0026]     In the melt spinning process, the molten polymer is extruded into air or other gases, or into a suitable liquid to quench and solidify the molten filaments. The solidification process is conducted by using quenching gas, usually cooling air, at a temperature of about 10-25° C. The setting of the temperature and the velocity of the quenching air blown to the molten filaments depend on the polymer and the filament properties desired. The filaments may be lubricated with oil at about 100-120 cm below the spinneret to facilitate solidification. The amount of oil (OPU, oil per unit) applied is about 0.5-0.8% and may vary depending on the polymer used and spinning conditions. Before being taken up, the filaments may be subjected to further processing such as drawing or texturing to achieve desired properties.  
         [0027]     The fibers or filaments produced by the above process have a regular polygonal cross-section, in which all sides are of approximately equal length. Preferably, variation of each side of the polygonal cross-section of the fabricated fiber is less than 50%, more preferably less than 5% from the mean value. The fibers of the invention can be employed in many applications, and are not limited to the fabrication of woven, non-woven, and knitted fabrics or clothes. The fibers of the invention are particularly suited for use in the fabrication of fabrics or textiles that require superior wind resistance, luster, and thermal insulation.  
         [0028]     The following examples are presented to further illustrate the invention and are not to be construed as limitations thereon.  
       EXAMPLE 1  
     The Preparation of PET Fiber Having Square Cross-section (1)  
       [0029]     A melt dope was prepared by melting regular polyester resin (R-PET) of intrinsic viscosity of 0.64 (manufactured by Shinkong Synthetic Fibers Co. Taiwan) at 285° C. The melt was then spun at 42.7 grams/minute through a spinneret having 48 contoured quasi-square orifices. The filaments extruded from the spinneret were then cooled by blowing with a quenching air of 16° C. at a velocity of 0.55 m/sec. After quenching, the filaments were treated with an aqueous liquid containing 10% oil by contacting an applicator located at a distance of 110 cm below the spinneret to facilitate the solidification of the hot filaments. The amount of oil applied onto the fiber was 0.83% of the fiber weight. The cooled and solidified filaments were then passed through a set of driven take-up rolls and winded up at a speed of 3200 meter/minute to obtain a partially oriented yarn (POY). The obtained yarn bundles have 48 filaments and 120 deniers in linear density. The partially oriented yarn is further drawn to become fully oriented yarn (FOY). The FOY bundles have 48 filaments and 75 deniers in linear density. The properties of POY and FOY yarns are summarized in Table 1. The cross-section of the resultant fiber is shown in  FIG. 1 .  
       EXAMPLE 2  
     The Preparation of PET Fiber Having Square Cross-section (2)  
       [0030]     A melt dope was prepared by melting regular polyester resin (R-PET) of intrinsic viscosity of 0.64 (manufactured by Shinkong Synthetic Fibers Co. Taiwan) at 285° C. The melt was then spun at 28.4 grams/minute through a spinneret having contoured quasi-square orifice. The filaments extruded from the spinneret were then cooled by blowing with a quenching air of 16° C. at a velocity of 0.45 meter/sec. After quenching, the filaments were treated with an aqueous liquid containing 10% oil by contacting an applicator located at a distance of 110 cm below the spinneret to facilitate the solidification of the hot filaments. The amount of oil applied onto the fiber was 0.81% of the fiber weight. The cooled and solidified filaments were then passed through a set of driven take-up rolls and winded up at a speed of 3200 meter/minute to obtain a partially oriented yarn (POY). The obtained yarn bundles have 48 filaments and 80 deniers in linear density. The partially oriented yarn is further drawn to become fully oriented yarn (FOY). The FOY bundles have 48 filaments and 50 deniers in linear density. The properties of POY and FOY yarns are summarized in Table 1 below.  
       COMPARATIVE EXAMPLE 1  
     The Preparation of PET Fiber Having Round Cross-section (1)  
       [0031]     A melt dope was prepared by melting regular polyester resin (R-PET) of intrinsic viscosity of 0.64 (manufactured by Shinkong Synthetic Fibers Co. Taiwan) at 285° C. The melt was then spun at 42.7 grams/minute through a spinneret with 48 round orifices. The filaments extruded from the spinneret were then cooled by blowing with a quenching air of 16° C. at a velocity of 0.55 meter/sec. After quenching, the filaments were treated with an aqueous liquid containing 10% oil by contacting an applicator located at a distance of 110 cm below the spinneret to facilitate the solidification of the hot filaments. The amount of oil applied onto the fiber was 0.83% of the fiber weight. The cooled and solidified filaments were then passed through a set of driven take-up rolls and winded up at a speed of 3200 meter/minute to obtain a partially oriented yarn (POY). The obtained yarn bundles have 48 filaments and 120 deniers in linear density. The partially oriented yarn is further drawn to become fully oriented yarn (FOY). The FOY bundles have 48 filaments and 75 deniers in linear density. The properties of POY and FOY yarns are summarized in Table 1.  
       COMPARATIVE EXAMPLE 2  
     The Preparation of PET Fiber Having Round Cross-section (2)  
       [0032]     A melt dope was prepared by melting regular polyester resin (R-PET) of intrinsic viscosity of 0.64 (manufactured by Shinkong Synthetic Fibers Co. Taiwan) at 285° C. The melt was then spun at 28.4 grams/minute through a spinneret with 48 round orifices. The filaments extruded from the spinneret were then cooled by blowing with a quenching air of 16° C. at a velocity of 0.45 meter/sec. After quenching, the filaments were treated with an aqueous liquid containing 10% oil by contacting an applicator located at a distance of 110 cm below the spinneret to facilitate the solidification of the hot filaments. The amount of oil applied onto the fiber was 0.81% of the fiber weight. The cooled and solidified filaments were then passed through a set of driven take-up rolls and winded up at a speed of 3200 meter/minute to obtain a partially oriented yarn (POY). The obtained yarn bundles have 48 filaments and 80 deniers in linear density. The partially oriented yarn is further drawn to become fully oriented yarn (FOY). The FOY bundles have 48 filaments and 50 deniers in linear density. The properties of POY and FOY yarns are summarized in Table 1.  
                                                                                               TABLE 1                                       Before drawing   After drawing                Linear   Tenacity   Elongation   Linear   Tenacity   Elongation           density   (g/d)   (%)   density   (g/d)   (%)                        Example (1)   120   d   2.64   123   75   d   4.79   34.5       square       Example (2)   80   d   2.53   121   50   d   4.57   32.1       square       Comp. Exam.   120   d   2.72   120   75   d   4.86   32.3       (1) round       Comp. Exam.   80   d   2.65   118   50   d   4.65   30.2       (2) round                 Note:            d: denier             
 
       EXAMPLE 3  
     The Preparation of PET Fiber with Regular Triangular Cross-section  
       [0033]     A melt dope was prepared by melting regular polyester resin (R-PET) of intrinsic viscosity of 0.64 (manufactured by Shinkong Synthetic Fibers Co. Taiwan) at 285° C. The melt was then spun at 28.4 grams/minute through a spinneret with 48 round orifices. The filaments extruded from the spinneret were then cooled by blowing with a quenching air of 16° C. at a velocity of 0.45 meter/sec. After quenching, the filaments were treated with an aqueous liquid containing 10% oil by contacting an applicator located at a distance of 110 cm below the spinneret to facilitate the solidification of the hot filaments. The amount of oil applied onto the fiber was 0.82% of the fiber weight. The cooled and solidified filaments were then passed through a set of driven take-up rolls and winded up at a speed of 3200 meter/minute to obtain a partially oriented yarn (POY). The obtained yarn bundles have 48 filaments and 80 deniers in linear density. The partially oriented yarn is further drawn to become fully oriented yarn (FOY). The FOY bundles have 48 filaments and 50 deniers in linear density. The cross-section of the resultant fiber is shown in  FIG. 2 .  
         [0034]     One of the unique characteristics of the fibers with equilateral polygonal cross section is related to stacking of the fiber. As shown in Table 2, in the case of the equilateral polygonal fiber, the wind resistance of the fabric, in terms of pressure drop at a certain air flux, is significantly higher than the fabrics made of conventional round fibers. Especially, the wind resistance of the fabric of square fiber is much higher than the fabrics made of triangular fibers. At higher air fluxes, the trends are the same with slightly different ratios. In some embodiments, the fabric of square fibers may have a wind resistance of more than 3 times higher than a fabric made of round fibers, and more than 50% higher than that of triangular fibers.  
         [0035]     It is surprising and unexpected that the square fiber results in remarkably higher wind resistance in fabrics as compared to triangular fiber, since it was originally held that the square fiber and triangular fiber would have the same packing behavior due to their flat surfaces.  
                                                           TABLE 2                           Comparison of wind resistance of PET woven fabrics                Air flux   Square fiber   Triangular   Round fiber           (l/min)   (mm H 2 O)   fiber (mm H 2 O)   (mm H 2 O)                            20   37   24   11           40   96   59   23           60   136   88   39           80   148   104   59           100   150   122   93                         Remarks□fiber spec: 50 d/48 f; fabric structure□1/1 plain weave, weft 200 threads/inch, warp 110 threads/inch.             
 
         [0036]     The luster, measured as the percentage of the light reflection from the fabric surface, is also shown in Table 3. Fabrics of both square and triangular fibers show higher luster than that of the round fiber. This is due to the light reflection from the flat surface of either the square or the triangular fiber. The fabric of square surface has the highest luster because of the better fiber stacking on the fabric surface, which results in a flatter and shinier surface. Specially, the fabric of square fibers has a luster of more than 2 times higher than that of round fibers, and surprisingly, more than 50% higher than that of triangular fibers.  
                                                                         TABLE 3                           Comparison of air permeability and luster of PET woven fabrics                Pressure   Square fiber   Triangular fiber   Round fiber                (Pa)   Air permeability (cc/cm 2 □ sec)                            25   0.132   0.160   0.188           50   0.169   0.224   0.279           75   0.198   0.336   0.474           100   0.240   0.520   0.660           125   0.276   0.575   0.773           150   0.331   0.691   0.850           Luster (%)   5.78   3.24   2.56                         Remarks□(1) Fiber spec.: 50 d/48 f; fabric structure□ 1/1 plain weave, weft 200 threads/inch, warp 110 threads/inch.                (2) Luster is measured in terms of light reflection from the fabrics. All fabrics are not colored.             
 
         [0037]     While the invention has been described by way of examples and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.