Abstract:
Method and apparatus for producing multi-segmented filaments are provided. In one embodiment a first polymer material is passed into a die, the first polymer material and the die being maintained under predetermined rheological conditions. Next, the first polymer material is extruded through a plurality of die openings in the die, the die openings arranged in a group, the group configured to form at least two elementary filaments. Then, the two elementary filaments are connected to one another by adhesion contact to form a multi-segmented filament. In another embodiment a die for producing multi-segmented filaments is provided. This die comprises a polymer source maintaining a polymer under predetermined rheological conditions. A die in communication with the polymer source, the die maintaining the polymer under predetermined rheological conditions and a die plate in fluid communication with the die, the die plate defining a first group of openings, the first group comprising a first opening and a second opening, the first opening and the second opening configured to form a first elementary fiber having a skin and a second elementary fiber having a skin.

Description:
CLAIM OF FOREIGN PRIORITY 
     This application claims priority to French Application No. FR P 9902601 filed on Mar. 1, 1999, and incorporates that application herein by reference. 
     FIELD OF THE INVENTION 
     The present invention regards man made filaments. More specifically the present invention regards method and apparatus for producing multi-segment filaments, multi-segment filaments themselves, and textiles formed with multi-segmented filaments. 
     BACKGROUND 
     Multi-segmented filaments are man made tendrils made from polymers. Numerous processes are presently known for the production of these multi-segmented filaments or fibers. Some of these known procedures extrude the filaments directly from the raw materials while others utilize recycled materials, such as non-woven textile surfaces, to create the multi-segmented filaments. In one known production process, thermoplastic polymer materials are co-extruded through divided spinning die openings to form the desired multi-segment filament forms. Such a process, however, results in mono-filaments, which suffer from numerous restrictions and disadvantages, being formed. For example, it is difficult to separate the multi-segment mono-filaments into more basic elementary filaments. If required, machines are utilized to attempt this separation. Unfortunately, these machines, which are not always successful in separating the filaments, are cumbersome as they must be able to develop significant concentrated forces in order to carry out the separation. In fact, in some circumstances, such as when the elementary filaments are formed from the same polymer or from chemically compatible polymers, their separation back into their original state is impossible to carry out. Similarly, when materials in their miscible state are used to create multi-segmented filaments, they, too, may also be impossible to separate into a filament state. 
     In addition, known technology only offers a limited number of shapes and titers for the manufacture of multi-segmented filaments due to: the complexity of the feed circulations in the dies; the low limit conditions of spinning and extrusion for the fine-titer filaments or fibers; the physical impossibilities that result from co-extrusion; and the exorbitant costs associated with manufacturing the required spinning dies. 
     Further to these obstacles, it is also not possible with current technologies, to achieve complex external cross-sections having clear outlines such as edges and notches. Due to the rheological properties of polymers these edges and notches fade during this known co-extrusion manufacturing process. 
     SUMMARY OF THE INVENTION 
     Multi-segmented filaments and method and apparatus for producing multi-segmented filaments are provided. In one embodiment a first polymer material is passed into a spinning die, the first polymer material and the spinning die being maintained under predetermined rheological conditions. Next, the first polymer material is extruded through a plurality of die openings in the die, the die openings arranged in a group, the group configured to form at least two elementary filaments. Then, the two elementary filaments are connected to one another by adhesion contact to form a multi-segmented filament. 
     In another embodiment a die for producing multi-segmented filaments is provided. This die comprises a polymer source maintaining a polymer under predetermined rheological conditions; a die in communication with the polymer source, the die maintaining the polymer under predetermined rheological conditions; and a die plate in fluid communication with the die, the die plate defining a first group of openings, the first group of openings comprising a first opening and a second opening, the first opening and the second opening configured to form a first elementary fiber having a skin and a second elementary fiber having a skin. 
     In yet another alternative embodiment a multi-segmented filament is provided. This filament comprises a first elementary fiber having a skin and a second elementary fiber having a skin. In this embodiment the first elementary fiber is connected longitudinally to the second elementary fiber by adhesion of the skin of the first elementary fiber with the skin of the second elementary fiber. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The various features of the invention will be best appreciated by simultaneous reference to the description which follows and the accompanying drawings in which: 
     FIG. 1 is a partial cross-sectional view of a die plate being operated in accord with a first embodiment of the present invention; 
     FIG. 2 is a cross-sectional view of a multi-segmented filament produced by the die plate of FIG. 1; 
     FIG. 3 is an enlarged view of the exit side of the die plate illustrated in FIG. 1; 
     FIG. 4 is an exit side view of a die plate in accordance with a second embodiment of the present invention; 
     FIG. 5 is an exit side view of a die plate in accordance with a third embodiment of the present invention; 
     FIG. 6 is an exit side view of a die plate in accordance with a fourth embodiment of the present invention; 
     FIG. 7 is an exit side view of a die plate in accordance with a fifth embodiment of the present invention; 
     FIG. 8 is an exit side view of the die plate of FIGS. 1 and 3 in accord with a first embodiment of the present invention; 
     FIG. 9 is an exit side view of a die plate in accordance with a sixth embodiment of the present invention; 
     FIG. 10 is a partial cross-sectional view of a die being operated in accord with a seventh embodiment of the present invention; and 
     FIG. 11 is a cross-sectional view of a multi-segmented fiber manufactured in accord with an eight embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 illustrates a die in accord with a first embodiment of the present invention. In FIG. 1 a die plate  100  having a first opening  140  and a second opening  145 , both of which penetrate through the die plate  100 , is shown. As is evident, the first opening  140  and the second opening  145  are equally sized and parallel to one another. As is also evident a point  110  located on the perimeter of the first opening  140  and a point  115  located on the perimeter of the second opening  145  are also illustrated in FIG.  1 . As will be discussed in more detail below, these points,  110  and  115 , mark the shortest distance between the two openings  140  and  145 . Therefore, the marker “d” in FIG. 1 marks the shortest distance between points  110  and  115  and concomitantly the shortest distance between the first opening  140  and the second opening  145 . Also illustrated in FIG. 1 is a polymer  180 , a first bead  150  and a second bead  155 , elementary filaments  160  and  165 , skins  170  and  175  and multi-segmented filament  120 . 
     In accord with the first embodiment of the present invention, the polymer  180  is fed into the spinning die under favorable rheological conditions, examples of which are provided below. After entering the spinning die the polymer  180 , is then extruded through both openings. These openings, the first opening  140  and the second opening  145 , are arranged as a group on the die plate  100  in order to form a set of two elementary filaments  160  and  165  when the polymer is drawn through the die. Once drawn through the die, these elementary filaments, in this case the first elementary filament  160  and the second elementary filament  165 , come in contact with one another and are adhered to one another through the adhesion contacts of their skins  170  and  175 . Once adhered, the two elementary filaments now constitute the multi-segmented filament  120 . By adhering the elementary filaments together through the adhesion of their skins  170  and  175  phase mixing of adjacent elementary filaments is reduced if not eliminated. Once drawn, this multi-segmented filament  120  is then consolidated with other multi-segmented filaments, stretched, and passed on to subsequent processing or treatment steps. These steps can include the production of thicker filaments, the spooling of the filaments, the combination of the filaments into cables, and the manipulation of the filaments into non-woven textiles. 
     Therefore, contrary to the current co-extrusion technology, in which the miscible phases of the various components come in contact with one another in a single opening for each multi-segmented filament, this first embodiment of the present invention extrudes the polymer through independent die openings  140  and  145 . Elementary filaments  160  and  165  are, therefore, formed independent of one another. These elementary filaments may make contact with one another after exiting the die openings  140  and  145  and, consequently, after their viscosities have begun to change and their phases have begun to be delimited by their skins  170  and  175 . 
     The multi-segmented filament  120  produced by this first embodiment has a cohesive force holding the elementary filaments  160  and  165  together. This cohesive force is derived from the adhesion contact of the border surface zones or skins of the elementary filaments while they were still sufficiently plastic and adherent to create an adhesive surface bond. Due to this adhesive surface bond, the phase mixing in the region of contact of the skins  170  and  175  can be sufficiently consolidated to be limited to the contact regions of the skins  170  and  175 . This adhesive surface bond can also be of sufficient strength to maintain the bond between elementary filaments over the course of subsequent treatments and processing. Conversely, these adhesive bonds may not be overly resilient as to prohibit later separation of the filaments as required in subsequent manufacturing steps. 
     The formation and dimensions of the beads  150  and  155  that form at the exit of the die openings are determined by: the shape and size of the die openings; by the type of polymer(s), or polymer solution(s) extruded from the die; by the pressure, the speed, and the rheological conditions of extrusion and spinning; and by the consolidation conditions. In addition, the bonding forces between elementary filaments can be adjusted by modifying the consolidation conditions. 
     FIG. 2 is a cross-section of a multi-segmented filament manufactured in accord with the methods defined in the first embodiment. As can be seen, this multi-segmented filament  120  has maintained the circular cross-sectional shape of the two elementary filaments that created it. 
     FIG. 3 is an enlarged view of the openings  140  and  145  in the spinning die plate  100 . As can be seen the openings are circular and points  110  and  115  have been identified in FIG. 3 on the circumference of these circular openings. As can also be seen points  110  and  115  mark the closest distance between the two circular openings. This distance is indicated by the lower case roman character “d” in FIG.  3 . 
     FIGS. 4-9 illustrate alternative embodiments of a die plate in accord with the present invention. While these alternative embodiments illustrate complex configurations that may be created in accord with the present invention they are merely examples of various configurations and should not be interpreted as an exclusive list. 
     FIG. 4 illustrates the exit face of die plate  400  in accord with a second embodiment of the present invention. As is evident die plate  400  has three oblong openings  410  which may be utilized to produce a three-lobed multi-segment filament. 
     FIG. 5 illustrates the exit face of die plate  500  in conformance to a third embodiment of the present invention. This die plate  500  has three openings  510  all of which comprise one group  520 . As is evident each of these openings  510  is circular and may be used to produce a multi-segmented filament in the shape of a strip or film that can be sectioned lengthwise. 
     FIG. 6 illustrates the exit face of die plate  600  in accord with a fourth embodiment of the present invention. As above, the exit face has a plurality of openings  610  and  620  which constitute one group. This die plate  600  may be used to produce a multi-segmented filament in the shape of a daisy. One advantage of this configuration is that the central opening  620  may be fed one polymer that can be used as a guide filament while the outer openings  610  can be fed a different polymer that may be used to customize the properties of the resulting multi-segmented filament. 
     FIG. 7 illustrates the exit face of die plate  700  in accord with a fifth embodiment of the present invention. This die plate  700  has a plurality of small circular openings  710  which may be used to produce a multi-segment filament in the shape of a hollow tube. 
     FIG. 8 illustrates the exit face of die plate  100 , which is discussed above. As is evident the openings are circular and are mirror images of one another about a center line  805 . 
     FIG. 9 illustrates the exit face of a die plate  900  in accord with a sixth embodiment of the present invention. This six embodiment has a first group of orifices  920  and a second group of orifices  910 . In use, this die plate may be used to produce a multi-segmented filament having two hollow tubes with different diameters and may be made of elementary filaments having different properties. 
     FIG. 10 illustrates a die plate  1080  in accord with the seventh embodiment of the present invention. As is evident the first opening  1010  and the second opening  1015  are not parallel to one another nor are they perpendicular to the exit face of the die. Also evident in FIG. 10 is: the first bead  1020 , the second bead  1025 , the skins  1030  and  1035 , the first elementary filament  1040 , the second elementary filament  1045 , and the multi-segmented filament  1000 . 
     As mentioned above, more than one polymer may be fed to and through the die plate  1080  of FIG.  10 . For example, in this seventh embodiment polymer  1022 , which is emerging from opening  1010 , is different from polymer  1021 , which is emerging from opening  1015 . By utilizing more than one polymer the adhesion qualities of the filaments and well as the final working properties of the multi-segment filament can be adjusted and modified. 
     FIG. 11 illustrates a cross-section of a multi-segmented filament made in accordance with an eight embodiment of the present invention. As is evident, the filament  1100  is clover shaped and comprises three prominent filaments. 
     Referring back now to FIG. 1, it has been found that for die openings having round or clearly circular cross-sections it is advantageous to have the distance (d) between die openings, in a group of die openings, satisfy the following equation with respect to another die opening in the group: 
     
       
         0.5×( D   n   +D   m )/2 ≦d ≦5×( D   n   +D   m )/2,  (equation 1) 
       
     
     where n is not equal to m, n varies from 1 to T, m varies from 1 to T, and where T is the total number of die openings of group G, D n  is the diameter of the first die opening, D m  is the diameter of the second die opening, and d is the distance between points  110  and  115  as illustrated in FIG.  1 . 
     In addition, regardless of their shape and using the same variable definitions, it has also been found that it is preferable that each die opening of a group of die openings, satisfies equation 2 with at least one other die opening of the same group: 
     
       
         0.5×( D   n   +D   m )/2 ≦d ≦2×( D   n   +D   m )/2.  (equation 2) 
       
     
     Two non-exhaustive, exemplary embodiments setting forth suggested rheological conditions are as follows. 
     EXAMPLE 1 
     A nonwoven material made of bisegmented endless filaments with a surface mass of 110 g/m 2  (NFG 38013) is first produced according to a process that is similar to the one described in the French Patent 7420254. 
     The configuration of the filaments making up the surface is based on a two-part fiber of 100% PES with a titer of 1.2 dTex before splitting (FIG. 2 is a view of the cross-section of these fibers). 
     The polymer used (POLYESTER) demonstrates the following properties: 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Substance 
                 polyethylene terephthalate 
               
               
                   
                 TiO 2   
                 0.4% 
               
               
                   
                 Melting point 
                 256° C. 
               
               
                   
                 Viscosity in the melted state 
                 210 Pa at 290° C. 
               
               
                   
                 Type and origin 
                 Type 20 from Hoechst 
               
               
                   
                   
               
             
          
         
       
     
     Conditions of Spinning Extrusion in Example 1 
     Drying takes place in dry air with a dew point of −40° C. with a dwell time of 3 hours at 170° C. The feed of the extruder takes place in air containing nitrogen. 
     The spinning unit is circular and contains a die plate that is composed of 240 groups of two openings spaced 0.15 mm apart, with a diameter of 0.2 mm and a height of 0.4 mm. 
     The melt-extrusion temperature of the polymer is 295° C., the spinning speed is around 4000 m/min, and the output per group is 0.5 g/min (0.25 g/min/capillary). 
     Consolidation—Bonding Criteria 
     The surface produced is subjected to hydraulic bonding under jets of 225 bar (twice per side), at a speed of 35 m/min, using spray nozzles of 130 microns. The initial filaments of 1.2 dTex are split into two identical parts of 0.6 dTex. 
     Characteristic Properties of the Filaments 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Titer (DIN 53812) 
                 1.2 
                 dTex 
               
               
                   
                 Strength 
                 27 
                 cN/Tex 
               
               
                   
                 Expansion 
                 78% 
                   
               
               
                   
                   
               
             
          
         
       
     
     Characteristic Properties of the Product 
     
       
         
               
               
               
               
             
           
               
                   
               
             
             
               
                 Dynamometry: 
                 Stress 
                 SL 350 
                 Algt SL 56% N/5 cm 
               
               
                   
                 Stress 
                 ST 300 
                 Algt SL 62% N/5 cm 
               
               
                   
                 Tear strength 
                 SL 35 N 
                 ST 55 N 
               
               
                   
                 (NFG07146) 
               
               
                   
                 Retraction 
                 SL-1.8% 
                 ST-2.1% 
               
               
                   
                 (180°/5 min) 
               
               
                   
               
             
          
         
       
     
     EXAMPLE 2 
     A non-woven material made of endless filaments with a surface mass of 130 g/m 2  is produced. 
     The configuration of the filaments making up the surface is based on a three-lobe distribution, proceeding from three capillaries that belong to one and the same group. FIG. 11 provides a cross-sectional view of these filaments. The three capillaries of one and the same feed die are arranged along the tips of an equilateral triangle with a side length of 0.4 mm. The diameter of a capillary is d=0.25 mm, its height is 2 d, the distance between two capillaries is 0.15 mm. 
     The polymer used and the extrusion/spinning conditions are identical with those of Example 1. 
     The output per group is 0.66 g/min (3×0.22 g) and the speed of spinning/stretching is approximately 4500 m/min, resulting in production of a filament at 1.5 dTex. 
     Consolidation—Fixing 
     The surface is subjected to double-sided needling at 200 perforations per cm 2 , using needles with a gauge of 40 RB that penetrate 12 mm. 
     Characteristic Properties of the Filaments 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Titer 
                 1.5 
                 dTex 
               
               
                   
                 Strength 
                 31 
                 cN/Tex 
               
               
                   
                 Expansion 
                 78% 
                   
               
               
                   
                   
               
             
          
         
       
     
     Characteristic Properties of the Product 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Stress 
                 SL 490 N/5 cm 
                 ST 370 N/5 cm 
               
               
                   
                 Expansion 
                 SL 60% 
                 ST 70% 
               
               
                   
                   
               
             
          
         
       
     
     Final Processing—Use 
     The product is then impregnated with an application of 480 g/m 2 , using a styrene-butadiene resin, and then calendared (calibrated). The end product is intended as reinforcement material for shoes. 
     Of course the invention is not limited to the implementations described above and shown in the attached drawings. Changes are possible without departing from the spirit and scope of the present invention. For example, although the above embodiments were explained in more detail with regards to hot extrusion of polymers in the melted state, it can also be used for dry spinning processes [solvent+polymer(s):extrusion with evaporation of the solvent] as well as for moist spinning processes [solvent+polymer(s) with die exit in the solvent bath of the solvent]. Moreover, changing the exit orifice diameters of adjacent openings in order to adjust the adhesion characteristics of the filaments may be done while nevertheless remaining within the scope of the present invention. Similarly, the shape of the bead can also be modified to reduce or change the adhesion contact point between the two elementary filaments and the openings may be separated to further adjust the size, shape or formation of the bead.