Patent Publication Number: US-2006008548-A1

Title: Spinneret plate for producing a bulked continuous filament having a three-sided exterior cross-section and a convex six-sided central void

Description:
CROSS REFERENCE TO RELATED APPLICATION  
      This application is a continuation-in-part of copending application Ser. No. 10/991,469, filed Nov. 19, 2004, which claims benefit of priority from Provisional Application No. 60/523,871 filed Nov. 19, 2003. 
    
    
     FIELD OF THE INVENTION  
      The present invention relates to a spinneret plate for producing a bulked continuous filament having an exterior configuration of three smoothly contoured sides with an inwardly extending depressed region located adjacent each tip of each side and with a convex, generally delta-shaped, six-sided central void extending therethrough.  
     DESCRIPTION OF THE PRIOR ART  
      While carpet yarns having relatively high levels of “glitter” have become fashionable there nevertheless remains a substantial demand for yarns which provide a lower glitter, more wool-like appearance with superior soil hiding, and which cover more surface area with lower face weights.  
      “Glitter” is the property of the yarn relating to the yarn&#39;s ability to reflect incident light. The amount of glitter exhibited by a yarn is a measure of the relative fraction of light that is reflected by the yarn. “Bulk” is the property of the yarn, which most closely correlates to surface coverage ability of a given yarn.  
      U.S. Pat. No. 3,329,553 (Sims et al.) discloses a trilobal filament having a void fraction in the range from ten to sixty-five percent (10-65%). This reference teaches that void ratio is correlated with bulk in that the higher the void ratio the greater the bulk.  
      U.S. Pat. No. 6,048,615 (Lin, RD-7395), assigned to the assignee of the present invention, discloses a trilobal filament with concave-sided voids formed from a thermoplastic synthetic polymer. This yarn exhibits excellent durability and good soiling resistance, but has relatively high glitter.  
      U.S. Pat. Nos. 5,108,838 and 5,176,926 (both to Tung), both assigned to the assignee of the present invention, disclose a solid trilobal filament formed from a thermoplastic synthetic polymer material which exhibits low glitter. The structure of this yarn provides less bulk and is somewhat less effective in hiding soil than the current invention.  
      U.S. Pat. No. 5,380,592 (Tung), assigned to the assignee of the present invention, discloses a trilobal cross-section with three voids which improve bulk and soil hiding compared to the solid cross-section trilobal filament discussed immediately above. However, this yarn is still somewhat vulnerable to soiling owing to the channels or “cusps” in the sides. Filaments of this yarn are also more subject to discontinuity in the spinning process owing to the complexity of the spinneret used to form the yarn. Open voids may occur in individual filaments, resulting in severe dyeability differences from filament to filament.  
      In view of the foregoing it is believed advantageous to provide a spinneret for forming synthetic filaments which is conducive to a stable spinning process that is consistent along the length of the filament and that produces filaments that are easily bulked, exhibit a relatively low glitter, and are contoured to resist soil accumulation.  
     SUMMARY OF THE INVENTION  
      The present invention is directed to a spinneret plate for producing a thermoplastic synthetic polymer filament having a three-sided exterior configuration wherein each side exhibits a smoothly curved contour having an inwardly extending depressed region disposed adjacent to each tip of each side. The filament has a generally delta-shaped void with a geometric center and three major apices extending centrally and axially therethrough. Each side of the void is convex in shape and has a first and a second end. Each side of the void is formed from two facets that meet to define a minor apex intermediate the first and second end of each side.  
      The spinneret plate has a cluster of three Y-shaped orifices centered about a central point. Each Y-shaped orifice has three linear legs meeting at a junction point. A connection point of the edges of the two legs, which is located in the straight line connecting the junction point and the central point, corresponds to a minor apex of the void. One leg of each orifice extends radially outwardly from the junction point, the axis of that one leg aligning with a radius extending outwardly from the central point. The axes of each of the other two legs of each orifice project toward an apex point disposed intermediate adjacent orifices, each intermediate point corresponding to a major apex of the void. The radially outwardly extending leg of each Y-shaped orifice is wider than the other legs of the Y-shaped orifice. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention will be more fully understood from the following detailed description, taken in connection with the accompanying drawings, which form a part of this application and in which:  
       FIG. 1  is a cross sectional view of a bulked continuous filament in accordance with the present invention;  
       FIG. 2  is a view of the bottom surface of a spinneret plate having a cluster of orifices formed therein for producing the filament shown in  FIG. 1 ;  
       FIG. 3  is a view of the bottom surface of a spinneret plate having a cluster of orifices formed therein for producing the filament shown in  FIG. 1 ;  
       FIG. 4  is a view of the bottom surface of a spinneret plate used for spinning the filaments of Comparative Example A; and  
       FIG. 5  is a view of the bottom surface of a spinneret plate used for spinning the filaments of Comparative Example B. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Throughout the following detailed description similar reference numerals refer to similar elements in all Figures of the drawings.  
       FIG. 1  is a cross section view of a bulked continuous filament generally indicated by reference character  10  in accordance with the present invention. A longitudinal axis  12  extending through the filament  10  serves its geometric center. The distance from the axis  12  to the point(s) on the exterior contour of the filament  10  closest to the axis defines the minor radius (R 1 ) of the filament. A major radius (R 2 ) is defined as the distance from the axis  12  to the point(s) on the exterior contour of the filament that lie farthest therefrom.  
      Each filament  10  has a generally three-sided exterior configuration formed from sides  14 A,  14 B and  14 C. The side  14 A is defined by a smoothly curved contour extending between a first rounded tip  16 A and a second rounded tip  16 B. The side  14 B is defined by a smoothly curved contour extending between the second rounded tip  16 B and a third rounded tip  16 C. The side  14 C is defined by a smoothly curved contour extending between the third rounded tip  16 B and the rounded first tip  16 A. The distance from a respective center of generation  18 A,  18 B,  18 C to each rounded tip  16 A,  16 B,  16 C is indicated by a tip radius R 3  (only one of which is illustrated in  FIG. 1  for clarity of illustration).  
      Each exterior side  14 A,  14 B,  14 C has a first inwardly extending depressed region  22  disposed near one tip and a second inwardly extending depressed region  24  disposed near the other tip. By “depressed region” it is meant that the contour of the filament in that region extends inwardly toward the axis  12  of the filament. The intermediate region  26  of each side  14 A,  14 B,  14 C (i.e., the region between the depressed regions  22 ,  24  on that side) is bowed slightly outwardly from the axis  12 . Each exterior side  14 A,  14 B,  14 C of the filament  10  thus exhibits a generally “wavy” configuration having two concave regions (i.e., the depressed regions  22 ,  24 ) and three convex regions (i.e., the bowed intermediate region  26  and the rounded regions  28  disposed near each rounded tip of each side).  
      In general a filament  10  in accordance with the present invention has an exterior modification ratio (R 2 /R 1 ) in the range from about 1.4 to about 2.5, and more particularly in the range from about 1.6 to about 1.8. In addition, the ratio of the major radius (R 2 ) to the tip radius (R 3 ) defines a tip ratio (R 2 /R 3 ) in the range from about 2.0 to about 10.0, and more particularly in the range from about 2.0 to about 8.0.  
      The filament  10  has a void  30  extending centrally and axially therethrough. The axis  12  defines the geometric center of the void. The central void  30  is a generally “delta-shaped” opening having three generally convex major sides  32 A,  32 B,  32 C. Adjacent pairs of major sides  32 A,  32 B,  32 C join at adjacent ends to define three major apices  34 A,  34 B,  34 C. In accordance with the present invention each side  32 A,  32 B,  32 C is itself configured from a pair of discernable facets  38 A,  38 B. The facets  38 A,  38 B may be planar in contour or may be gently curving to approximate a planar contour. The facets  38 A,  38 B meet to define a minor apex  40 A,  40 B,  40 C located intermediate the ends of each respective major side  32 A,  32 B,  32 C. The major apices  34 A,  34 B,  34 C lie a distance R M  from the geometric center  12  of the void  30  while the minor apices  40 A,  40 B,  40 C are spaced a distance R m  from the same point. The ratio of the distance (R M ) to the distance (R m ) defines an apex ratio (R M /R m ) in the range from about 1.0 to about 1.55, and more particularly in the range 1.05 to 1.50.  
      The void  30  may occupy from about one percent (1%) to about twenty-five percent (25%), and more particularly from about one percent (1%) to about fifteen percent (15%), of the cross sectional area of the filament  10 .  
      In accordance with the present invention the central void  30  is oriented within the filament  10  such that each major apex  34 A,  34 B,  34 C of the void  30  extends toward the approximate midpoint of the respective proximal side  14 A,  14 B,  14 C of the filament  10 , while each minor apex  40 A,  40 B,  40 C extends toward the respective proximal rounded tip  16 A,  16 B,  16 C.  
      These relationships are exemplified in  FIG. 1  by the radial reference line  42  extending from the axis  12  of the filament  10  through the major apex  34 C and a point  44  disposed substantially midway along the intermediate region  26  of the side  14 C. Similar reference lines, omitted for clarity, may be drawn through the other major apices  34 A,  34 B and a substantial midpoint of the intermediate region on the respective proximal sides  14 A,  14 B of the exterior of the filament  10 . The alignment of the minor apices and the rounded tip of the filament are exemplified in  FIG. 1  by a radial reference line  46  extending from the axis  12  of the filament  10  through the minor apex  40 C and the rounded tip  16 C of the filament. Similar reference lines, again omitted for clarity, may be drawn through the minor apices  40 A,  40 B and the respective rounded tips  16 A,  16 B of the filament.  
      A filament in accordance with the present invention is a bulked continuous filament prepared using a synthetic, thermoplastic melt-spinnable polymer. Suitable polymers include polyamides, polyesters, and polyolefins. The polymer is first melted and then is extruded (“spun”) through a spinneret plate  50  having appropriately sized orifices therein (to be described hereinafter) under conditions which vary depending upon the individual polymer thereby to produce a filament  10  having the desired denier, exterior modification ratio, tip ratio, apex ratio and void percentage. The filaments are subsequently quenched by air flowing across them at a flow rate of between 1.2-1.8 ft/sec (0.36 to 0.55 m/sec). Void percentage can be increased by more rapid quenching and increasing the melt viscosity of thermoplastic melt polymers, which can slow the flow allowing sturdy pronounced molding to occur.  
      A plurality of filaments  10  are gathered together to form a yarn. Drawing and bulking of the combined filaments is performed by any method known in the art, with the preferred operating condition described below in the examples provided.  
      Owing to the particular desired properties of the filaments  10  a yarn formed therefrom is believed to be particularly advantageous for tufting [with other types of yarn(s), if desired] into carpet having especially desirable properties. If desired, the yarn could include other forms of filament(s).  
       FIG. 2  illustrates one example of a spinneret plate  50  useful for producing a filament  10  in accordance with the present invention.  
      The spinneret plate  50  is a relatively massive member having an upper surface (not shown) and a bottom surface  52 . As is well appreciated by those skilled in the art a portion of the upper surface of the spinneret plate is provided with a bore recess (not shown) whereby the plate  50  is connected to a source of polymer. Depending upon the rheology of the polymer being extruded the lower margins of the bore recess may be inclined to facilitate flow of polymer from the supply to the spinneret plate.  
      A plurality of capillary openings each generally indicated by the reference character  54  extends through the plate  50  from the recessed upper surface to the bottom surface  52 . Each capillary opening  54  serves to form one filament. Only one such capillary opening  54  is illustrated in  FIG. 2 . The number of capillary openings provided in a given plate thus corresponds to the number of filaments being gathered to form a predetermined number of yarn(s). As noted, additional filaments (if used) may be incorporated into the yarn in any convenient manner.  
      As best seen in  FIG. 2 , in the present invention each capillary opening  54  is itself defined by a cluster of three orifices  56 - 1 ,  56 - 2  and  56 - 3  centered symmetrically about a central point  58 .  
      Each orifice  56 - 1 ,  56 - 2  and  56 - 3  is a generally “Y”-shaped opening comprising three linear legs  62 A,  62 B and  62 C. Each leg  62 A,  62 B and  62 C has a respective longitudinal axis  64 A,  64 B,  64 C extending therethrough. The axes  64 A,  64 B,  64 C are angularly spaced from each other by one hundred twenty degrees (120°). The axes  64 A,  64 B,  64 C of the legs  62 A,  62 B and  62 C of each orifice intersect at a junction point  68 . The junction points  68  are spaced a distance  70  from the center point  58  of the cluster.  
      The orifices  56 - 1 ,  56 - 2  and  56 - 3  are arranged with respect to each other such that one leg of each orifice  56 - 1 ,  56 - 2  and  56 - 3 , e.g., the leg  62 A, extends from the junction point  68  in a radially outward direction relative to the central point  58 . Stated alternatively, the radially outwardly extending leg  62 A of each orifice  56 - 1 ,  56 - 2  and  56 - 3  is oriented such that its axis  64 A aligns with a radius  70  extending outwardly from the central point  58 . The edges of the legs  62 B and  62 C of each orifice intersect at a connection point  82 . The connection point  82  is located in the straight line (i.e. the axe  64 A) connecting the junction point  68  and the center point  58 . Each connection point  82  of the orifices  56 - 1 ,  56 - 2 ,  56 - 3  respectively corresponds to a minor apex  40 A,  40 B,  40 C of the void  30  of the filament being spun.  
      The other two legs  62 B,  62 C of each orifice  56 - 1 ,  56 - 2  and  56 - 3  are arranged such that the axes  64 B,  64 C thereof project toward an apex point  72  disposed intermediate adjacent orifices. Extensions of each of the axes  64 B,  64 C of these legs  62 B,  62 C intersect at an apex point  72 . Each apex point  72  corresponds to a respective major apex  34 A,  34 B,  34 C of the void  30  of the filament being spun. The ends of the confronting legs  62 B,  62 C are spaced from each other by a gap  74 A,  74 B,  74 C. The legs  62 A,  62 B,  62 C of each of Y-shaped orifice  56 - 1 ,  56 - 2  and  56 - 3 , when measured along their respective axes, may or may not be equal in length. The length dimensions of the legs  62 A,  62 B,  62 C are indicated by the respective reference character A 1 , A 2 , A 3 .  
      The width dimensions of the legs  62 A,  62 B,  62 C are indicated by the respective reference character B 1 , B 2 , B 3 . The width dimension of the radially extending leg  62 A (indicated by the reference character B 1 ) is wider than the width dimensions (indicated by the reference characters B 2 , B 3 ) of the other legs  62 B,  62 C.  
       FIG. 3  illustrates another example of a spinneret plate  50  useful for producing a filament  10  in accordance with the present invention. One capillary opening  54  shown in  FIG. 3  is the same as in  FIG. 2  except for one of the tips of each orifice  56 - 1 ,  56 - 2 , and  56 - 3 . There is an extended circular tip located along the radially extending leg  62 A in each orifice. The reference character D indicates the diameter of the extended circular tip of the extending leg  62 A. The ratio of the diameter D of the extended circular tip to the width B 1  of the dimension of the radially extending leg  62 A is about 1.0 to about 4.0.  
      The spinneret plate may be fabricated in any appropriate manner, as by using the laser technique disclosed in U.S. Pat. No. 5,168,143, (Kobsa et al., QP-4171-A), assigned to the assignee of the present invention.  
      The following Table presents the magnitudes of the various dimensions A 1 , A 2 , A 3 , B 1 , B 2 , B 3 , and D used to fabricate filaments having the cross section illustrated in  FIG. 1  used in invention Examples 1-3. The dimensions are in centimeters.  
                                       TABLE 1                                   A 1     A 2 , A 3     B 1     B 2 , B 3     D                                                            Invention   0.0389   0.0389   0.019   0.015   N/A       Example 1       Invention   0.054   0.054   0.013   0.011   N/A       Example 2       Invention   0.0508   0.0389   0.0185   0.0155   0.0381       Example 3                  
 
      Trilobal cross sections with voids (hollow filament) have been practiced in the past [e.g., U.S. Pat. No. 6,048,615 (Lin)]. However, hollow filament yarns are difficult to make because of cross section shape control. Void percent and exterior modification ratio are both sensitive to polymer viscosity and quench air flow. As is well understood by one skilled in the art, without tight control of these parameters, lack of cross section shape uniformity can result in streaks when the yarns are finally tufted into a carpet.  
      The combination of the three orifices taken together with the enlarged width dimension (B 1 ) of the radially outwardly extending leg of each orifice causes polymer streams emanating from each orifice to converge, thus producing surprisingly stable polymer flow that is less prone to filament breakage and process interruption than the more complicated spinnerets of the prior art.  
      The stable polymer flow provided by the use of the spinneret in accordance also results in surprising robustness of cross section formation in the spinning process. The fiber cross section shape is measurably less sensitive to quench airflow, and thus provides a distinct advantage versus the prior art as a result of the greater consistency of shape provided along the length of the formed filaments and yarns made therefrom.  
      In addition, the disclosed spinneret plate is especially useful in the manner of producing the disclosed filament cross-section because it is simpler and less expensive to produce than previous hollow filament spinnerets.  
     EXAMPLES  
      Spinning Process:  
      Nylon 6,6 filaments having various cross-sections were produced for Comparative Examples A and B and for Invention Examples 1-3 from appropriately configured spinnerets, each with one hundred thirty-six (136) capillaries.  
      The nylon 6,6 polymer used for all of the examples was a bright polymer. The polymer spin dope did not contain any delusterant and had a relative viscosity (RV) of sixty-eight plus/minus approximately three units (68, ±˜3 units). The polymer temperature before the spinning pack was controlled at about two hundred ninety plus/minus one degree Centigrade (290, ±1° C.). The spinning throughput was seventy pounds (70 lbs; 31.8 kg) per hour.  
      The relative viscosity (RV) was measured by dissolving 5.5 grams of nylon 6,6 polymer in fifty cubic centimeters (50 cc) of formic acid. The RV is the ratio of the absolute viscosity of the nylon 66/formic acid solution to the absolute viscosity of the formic acid. Both absolute viscosities were measured at twenty-five degrees Centigrade (25° C.).  
      The polymer was extruded through the different spinnerets and divided into two (2) sixty-eight filament (68) segments. The capillary dimensions for the spinnerets are described below. The molten fibers were then rapidly quenched in a chimney, where cooling air at about nine degrees Centigrade (˜9° C.) was blown past the filaments at three hundred cubic feet per minute [300 cfm (732 m/min)] through the quench zone. The filaments were then coated with a lubricant for drawing and crimping. The coated yarns were drawn at 2197 yards per minute (2.75×draw ratio) using a pair of heated draw rolls. The draw roll temperature was one hundred ninety degrees Centigrade (190° C.). The filaments were then forwarded into a dual-impingement hot air bulking jet similar to that described in Coon, U.S. Pat. No. 3,525,134 (Coon, assigned to the assignee of the present invention) to form two (2) twelve hundred five denier (1205 denier, 1340 decitex), 17.7 denier per filament (dpf) yarns (19 decitex per filament). The temperature of the air in the bulking jet was two hundred twenty degrees Centigrade (220° C.).  
      The spun, drawn, and crimped bulked continuous filament (BCF) yarns were cable-twisted to 3.2 turns per inch (tpi) on a cable twister and heat-set on a Superba heat-setting machine at setting temperature of two hundredt sixty degrees Farenheit (265° F.; 129.4° C.).  
      The yarns were then tufted into twenty-eight ounce per square yard (28 oz/sq.yd; 949 g/sq. meter) having 0.21875 inch [7/32″, 0.56 cm] pile height loop pile carpets on a  1 / 10  inch gauge (0.254 cm) loop pile tufting machine. The tufted carpets were dyed on a continuous range dyer into medium yellow carpets.  
      Test Methods:  
      Each carpet sample produced from the yarns of Comparative Examples A and B and Invention Examples 1-3 was subjected to the following tests.  
      Carpet Glitter and Bulk Ratings  
      The degrees of bulk and glitter for different cut-pile carpet samples were visually compared in a side-by-side comparison without knowledge of which carpets were made with which yarns. The carpets were examined by a panel of five (5) experienced examiners each familiar with carpet construction and surface texture. The glitter value was measured by the examiners on a scale of “1” to “5”, with “5” being the most glitter. The glitter rating for each sample was averaged and the samples given a rating of low, medium or high glitter based on the average rating. Carpet bulk was rated in the same manner. The glitter and bulk results are reported in Table 2.  
      Soiling Test  
      The soiling test was conducted on each carpet sample using a Vetterman drum.  
      The base color of the sample was measured using the hand held color measurement instrument sold by Minolta Corporation as “Chromameter” model CR-210. This measurement was the control value.  
      The carpet sample was placed in Vetterman drum. Two hundred grams (200 g) of clean nylon 101 Zytel nylon beads and fifty grams (50 g) of dirty beads (by DuPont Canada, Mississauga, Ontario) were placed on the sample. The dirty beads were prepared by mixing ten grams (10 g) of AATCC TM-122 synthetic carpet soil (by Manufacturer Textile Innovators Corp. Windsor, N.C.) with one thousand grams (1000 g) of new Nylon 101 Zytel beads. Sixteen to seventeen hundred grams (1600-1700 g) of ceramic cylindrical shaped beads [110 to 130 ½″ diameter×½″ length small beads and twenty-five to thirty-five (25 to 35) ¾″ diameter, ¾″ length (1.91 cm diameter, 1.91 cm length) large beads were added into the Vetterman drum. The Vetterman drum was run for five hundred (500) cycles and the sample removed.  
      The color of the sample was again measured and the color change versus the control value (delta E) owing to soiling was recorded as an “As Soiled” value [note: This interim result is not reported in Table 2]. The sample was vacuumed four (4) times in both the length and width directions and the color was again measured and the color change versus control value (delta E) after vacuuming was recorded as an “As Cleaned” value [note: This interim result is not reported in Table 2].  
      The sample was placed back in the drum, fifty grams (50 g) of soiled bead mixture was discarded and fifty grams (50 g) of new dirty beads were added into the drum.  
      The procedure described above was repeated for three additional five hundred (500) cycle runs.  
      After a total of two thousand (2000) cycles, the color of the sample versus the control value (delta E) “As Soiled” was measured and reported. The color change versus the control value after vacuuming (the “As Cleaned” value) was measured and recorded. These measurements (i.e., the “As Soiled” and the “As Cleaned” values taken after two thousand cycles) are reported in Table 2 in the columns “As Soiled” and “As Cleaned”, respectively. Samples with a high value of delta E perform worse than samples with low delta E value.  
     Comparative Example A  
      Filaments having a trilobal cross-section as disclosed in U.S. Pat. No. 4,492,731 (Bankar et al.), assigned to the assignee of the present invention, were made using the above-described spinning process. The filaments were spun through a spinneret capillary as shown in  FIG. 4  having three tapered arms (lobes) which were essentially symmetrical.  
     Comparative Example B  
      Filaments having a hollow trilobal cross section as disclosed in U.S. Pat. No. 6,048,615 (Lin), assigned to the assignee of the present invention, were made using the above-described spinning process. The filaments were spun through a spinneret capillary as shown in  FIG. 5 .  
     Invention Example 1  
      Filaments having a hollow trilobal cross section as described by this invention, as shown in  FIG. 1 , were made using the above-described process. The filaments were spun through a spinneret capillary as shown in  FIG. 2 . The dimensions of the capillary used to produce Invention Example 1 are as set forth in Table 1.  
      The filament had an exterior modification ratio of 1.66, a tip ratio of 5.2, an apex ratio of 1.08. The central void occupied about 5.3 percent of the cross sectional area of the filament.  
     Invention Example 2  
      Filaments having a hollow trilobal cross section as described by this invention, as shown in  FIG. 1  were made using the above-described process. The filaments were spun through a spinneret capillary as shown in  FIG. 2 . The dimensions of the capillary used to produce Invention Example 2 are as set forth in Table 1.  
      The filament had an exterior modification ratio of 1.88, a tip ratio of 7.0, an apex ratio of 1.33. The central void occupied about ten percent (10%) of the cross sectional area of the filament.  
     Invention Example 3  
      Filaments having a hollow trilobal cross section as described by this invention, as shown in  FIG. 1 , were made using the above-described process. The filaments were spun through a spinneret capillary as shown in  FIG. 3 . The dimensions of the capillary used to produce Invention Example 3 are as set forth in Table 1.  
      The filament had an exterior modification ratio of 2.0, a tip ratio of 3.8, an apex ratio of 1.25. The central void occupied about one percent (1%) of the cross sectional area of the filament. The carpet yarns made in the example have wool-like appearance and excellent soiling and cleaning characteristics.  
      The test results are summarized below in Table 2.  
                                   TABLE 2                               Soiling   Soiling                   Cross-   (ΔE)   (ΔE)       Example   section   As Soiled   Cleaned   Glitter   Bulk                  Comp. A   Solid trilobal   23.25   21.14   High   High           (2.6 MR)       Comp. B   Hollow   N/A   N/A   High   Medium           trilobal       Inv. 1   1.66   17.94   16.71   Low   Medium       Inv. 2   1.88   21.17   19.86   Low   High       Inv. 3   2.00           Low   Medium                  
 
      As can be appreciated from Table 2, Examples 1-3 (having relatively “wavy” sides including two concave and three convex surfaces and a void shaped and oriented in the manner shown in  FIG. 1 ) demonstrate distinctly different and lower “Glitter” in the final carpet than do Comparative Examples A and B. The filament and yarn of the present invention is useful as a carpet yarn having more “wool-like” appearance when made into carpet than yarns of the prior art having similar bulk, soiling and cleaning characteristics.  
      The filament of the invention is also smoother (i.e., with rounded tips and without sharply defined cusps) and therefore less prone to soiling than other known high bulk trilobal fibers that can otherwise impart similar aesthetics to a carpet made therefrom, as is clearly supported by the soiling data in Table 2. A carpet constructed from yarn of the present invention therefore retains its appearance longer in service than carpets made from yarn of the prior art.  
      To achieve high bulk with low glitter is generally believed to be difficult. The invention provides a surprisingly low glitter yarn that can produce carpets of comparable bulk to carpets made from such high glitter yarns as the solid trilobal cross section filaments (Comparative Example A).  
      As a result of the configuration filaments in accordance with this invention and yarns formed therefrom are easily bulked and exhibit a relatively low glitter while the exterior contour resists soil accumulation.