Abstract:
The invention provides an improved method for making a poly(ester) bicomponent fiber wherein at least one poly(ester) contains a styrene polymer.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to bicomponent filaments, particularly to a process for making bicomponent filaments, more particularly to a process wherein such bicomponent filaments contain a small amount of styrene polymer additive.  
           [0003]    2. Discussion of Background Art  
           [0004]    Spinning of bicomponent polyester fibers has been disclosed in U.S. Pat. No. 3,671,379 (which shows a ‘snowman’ fiber cross-section in FIG. 4), Published World Patent Application WO2001-53573 and Published United States Patent Application US2001-0055683. Spinning polyester fiber containing polystyrene has been disclosed in Published Japanese Patent Application JP56-91013 and U.S. Pat. No. 4,424,258. Published Japanese Patent Application JP57-61716, misquoted in published Published Japanese Patent Application JP59-26524, discloses the use of blends of polyesters with polyacrylates, polystyrene, or polymethacrylates to make mixed filaments, in which two polymer streams are spun simultaneously but separately to form two distinct groups of different filaments. The latter application teaches away from using such blends to make side-by-side bicomponent fibers. Published Japanese Patent Application JP11-189925 discloses spinning and twisting a fiber having a small core of polystyrene/polyester blend in a sheath of the same polyester in order to avoid reported “melt fusion” in subsequent processing.  
           [0005]    There remains a need to make high-crimp, side-by-side, bicomponent fibers at high speeds.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention provides a process for making a side-by-side bicomponent filament comprising the steps of:  
           [0007]    a) providing poly(trimethylene terephthalate);  
           [0008]    b) providing a polyester selected from the group consisting of poly(ethylene terephthalate) and copolyesters of poly(ethylene terephthalate), in a weight ratio of about 30/70 to 70/30;  
           [0009]    c) providing a styrene polymer having a number-average molecular weight of about 75,000 daltons to 300,000 daltons;  
           [0010]    d) mixing the styrene polymer with at least one of the poly(trimethylene terephthalate) of step (a) and the selected polyester of step (b) to form a first melt-extrusion polymer and a second melt-extrusion polymer, respectively, wherein at least one melt-extrusion polymer contains from about 0.1 weight percent to about 5 weight percent styrene polymer;  
           [0011]    e) melting the first melt-extrusion polymer;  
           [0012]    f) melting the second melt-extrusion polymer;  
           [0013]    g) spinning the first and second melt-extrusion polymers into a filament;  
           [0014]    h) quenching the filament with gas in a manner selected from the group consisting of cross-flow and co-current flow;  
           [0015]    i) withdrawing the filament; and  
           [0016]    j) winding up the filament. 
       
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0017]    [0017]FIG. 1 shows a quench system that can be used in a process of the invention.  
         [0018]    [0018]FIG. 2 shows a roll system that can be used in a process of the invention.  
         [0019]    [0019]FIG. 3 illustrates fully drawn filament crimp values obtained at various windup speeds in a process of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]    In contrast to the disclosures of the prior art, it has now been found that side-by-side bicomponent filaments comprising poly(ethylene terephthalate) and poly(trimethylene terephthalate) with a small amount of styrene polymer additive can be spun at unexpectedly high speeds without sacrificing desirable crimp. In further contrast to the prior art, no melting or sticking was observed during processing of the filament, for example during drawing, winding, testing, and the like, even when no particular precaution was taken to prevent the polystyrene from being present at the surface of the filament. As a result of the high degree of crimp in the filament, it was not necessary to twist the filament to make it useful.  
         [0021]    As used herein, “bicomponent filament” means a continuous filament comprising polyesters of different chemical composition, specifically poly(ethylene terephthalate) and poly(trimethylene terephthalate), adhered to each other along the length of the filament in a side-by-side relationship. “Withdrawal speed” means the speed of the feed rolls, which are positioned between the quench zone and the (optional) draw rolls and is sometimes referred to as the spinning speed. “IV” means intrinsic viscosity. “Fully drawn” filament means a bicomponent filament which is suitable for use, for example, in weaving, knitting, and preparation of nonwovens without further drawing and can exhibit useful crimp contraction values. “Partially oriented” filament means a filament which has considerable but not complete molecular orientation, for example having considerable residual draw, and which generally requires drawing or draw-texturing before it is suitable for weaving or knitting and before it can exhibit useful crimp contraction values. “Fully oriented” filament means a filament which, as-spun, requires no drawing to be useful or to exhibit useful crimp contraction values. “Co-current gas flow” means a flow of quench gas which is accelerated in the direction of filament travel.  
         [0022]    In the process of the present invention, a small amount of styrene polymer additive is mixed with at least one of a) poly(trimethylene terephthalate) and b) poly(ethylene terephthalate) or copolyesters of poly(ethylene terephthalate). The mixture can be made by ‘salt-and-pepper’ blending, optionally followed by compounding, for example in an extruder. The poly(ethylene terephthalate) or copolyester thereof, or mixture of styrene polymer with poly(ethylene terephthalate) or copolyester thereof (the ‘second melt-extrusion polymer’), is then melt-spun with poly(trimethylene terephthalate) or mixture of styrene polymer and poly(trimethylene terephthalate) (the ‘first melt-extrusion polymer’) in a weight ratio of 70/30 to 30/70 to form a side-by-side bicomponent filament, and the filament is quenched, withdrawn, and wound up. The styrene polymer is present in one component, and can be present in both components, of the bicomponent filament. The styrene polymer additive is present at a level of 0.1 to about 5 weight percent, typically about 0.5 to about 4 weight percent, based on weight of the mixture.  
         [0023]    The poly(ethylene terephthalate) or copolyester thereof can have an IV of about 0.45-0.80 dl/g and the poly(trimethylene terephthalate) can have an IV of about 0.85-1.50 dl/g. A copoly(ethylene terephthalate) can be used in which the comonomer used to make the copolyester is selected from the group consisting of linear, cyclic, and branched aliphatic dicarboxylic acids having 4-12 carbon atoms (for example butanedioic acid, pentanedioic acid, hexanedioic acid, dodecanedioic acid, and 1,4-cyclo-hexanedicarboxylic acid); aromatic dicarboxylic acids other than terephthalic acid and having 8-12 carbon atoms (for example isophthalic acid and 2,6-naphthalenedicarboxylic acid); linear, cyclic, and branched aliphatic diols having 3-8 carbon atoms (for example 1,3-propane diol, 1,2-propanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-1,3-propanediol, and 1,4-cyclohexanediol); and aliphatic and araliphatic ether glycols having 4-10 carbon atoms (for example, hydroquinone bis(2-hydroxyethyl) ether, or a poly(ethyleneether) glycol having a molecular weight below about 460, including diethyleneether glycol). The comonomer can be present in the copolyester at levels of about 0.5-15 mole percent. Isophthalic acid, pentanedioic acid, hexanedioic acid, 1,3-propane diol, and 1,4-butanediol are preferred.  
         [0024]    Either or both polyesters can contain minor amounts of other comonomers, provided such comonomers do not have an adverse affect on the spinning speed, filament crimp value, or other properties. Such other comonomers include 5-sodium-sulfoisophthalate, at a level of about 0.2-5 mole percent, and very small amounts of trifunctional comonomers such as trimellitic acid. Poly(ethylene terephthalate) and poly(trimethylene terephthalate) include such copolyesters thereof within their meaning  
         [0025]    The styrene polymer additive has a number average molecular weight of at least about 75,000 daltons, typically at least about 100,000 daltons and at most about 300,000 daltons, more typically at most about 200,000 daltons. Useful styrene polymers can be isotactic, atactic, or syndiotactic; especially at higher molecular weights, atactic is preferred. The styrene polymer can be selected from the group consisting of polystyrene, alkyl- or aryl-substituted polystyrenes (for example prepared from □-methylstyrene, p-methoxystyrene, and vinyltoluene), copolymers of styrene and substituted styrene, and styrene multicomponent polymers such as styrene-butadiene copolymers. Polystyrene (“PS”) is preferred.  
         [0026]    The poly(trimethylene terephthalate) (“3G-T”), poly(ethylene terephthalate) (“2G-T”), styrene polymer additive, and/or the mixtures thereof, can, if desired, contain additives, such as delusterants, nucleating agents, heat stabilizers, viscosity boosters, optical brighteners, pigments, and antioxidants. For example, TiO 2  or other pigments can be added to the poly(trimethylene terephthalate), the poly(ethylene terephthalate), the styrene polymer additive, the mixture(s), or during filament manufacture.  
         [0027]    After being spun from a spinneret, the hot filament can be quenched with a gas supplied as cross-flow or co-current flow. In cross-flow, the gas can be blown across the just-spun filaments, for example from one side of a quench chamber as shown in FIG. 1. In co-current flow, quench gas can be introduced from above, for example from an annular space around the spinneret, or from the side as shown in FIG. 2 of U.S. Pat. No. 5,824,248 and FIGS. 2, 4, and  6  of Published United States Patent US-2002-0025433, which are incorporated herein by reference. The quench gas can be accelerated in the direction of filament travel, for example by supplying the gas at elevated pressure and using a constriction below the quench chamber through which both the gas and the filaments pass. The resulting superatmospheric pressure can be in the range of about 0.5-5.0 inches of water (about 1.3×10 −3  to 1.3×10 −2  kg/cm 2 . The maximum velocity of the quench gas is generally at the narrowest point of the constriction. When a constriction having a minimum inner diameter of one inch (2.54 cm) is used, the maximum gas velocity can be in the range of about 330-5,000 meters/minute. Subatmospheric pressure can also be used. Optionally, a flow of quench gas into each of two substantially coaxial quench chambers arranged in series along the path of the filaments and each chamber provided with a constriction through which gas and filaments pass, can be used.  
         [0028]    In one embodiment of the invention, the spun filament is drawn by about 2.0X to 4.5X and heat-treated at about 140° C. to 185° C. to form a fully-drawn filament before being wound up. When the quench gas is supplied as cross-flow, the windup speed is at least about 4100 m/min, typically about 5300 to 5800 m/min. When the quench gas is supplied as co-current flow, the windup speed is at least about 6200 m/min, preferably about 8200 to 9000 m/min. Such a filament can have an after-heat-set crimp contraction value of at least about 30%.  
         [0029]    In another embodiment of the invention, the filament is spun with quench gas supplied as cross-flow at withdrawal speeds of about 3000 to 4500 m/min, typically about 3500 to 4500 m/min, or as co-current flow at withdrawal speeds of about 3600 to 5000 m/min, typically about 4100 to 5000 m/min and wound up as a partially oriented filament, for example with little or no drawing. The partially oriented filament can be further processed later, for example drawn by about 2.0X to 4.5X and heat-treated at about 140° C. to 185° C., typically within about 35 days. At lower withdrawal speeds but still within the scope of the present invention, shorter delays between spinning and drawing/heat-treating would typically be used.  
         [0030]    In yet another embodiment, the filament is spun with cross-flow quench at withdrawal speeds of at least about 6000 to 8000 m/min and a fully oriented filament is wound up at substantially the same speed. Such filament typically has an after-heat-set crimp contraction value of at least about 30%.  
         [0031]    Higher levels of styrene polymer additive generally permit higher withdrawal and windup speeds, as does the use of styrene polymer additive mixed into both the poly(ethylene terephthalate) (or copolyester thereof) and the poly(trimethylene terephthalate).  
         [0032]    The filaments can have cross-sections that are round, ‘snowman’, octalobal, scalloped oval, trilobal, tetra-channel (also known as quatra-channel), and the like.  
         [0033]    The crimp values of the bicomponent filaments made in the Examples was measured as follows. Each sample was formed into a skein totaling 5000+/−5 denier (5550 dtex) with a skein reel at a tension of about 0.1 gpd (0.09 dN/tex). The skein was conditioned at 70+/−2° F. (21+/−1° C.) and 65+/−2% relative humidity for a minimum of 16 hours. The skein was hung substantially vertically from a stand, a 1.5 mg/den (1.35 mg/dtex) weight (e.g. 7.5 grams for a 5550 dtex skein) was hung on the bottom of the skein, the weighted skein was allowed to come to an equilibrium length, and the length of the skein was measured to within 1 mm and recorded as “C b ”. The 1.35 mg/dtex weight was left on the skein for the duration of the test. Next, a 500 gram weight (100 mg/d; 90 mg/dtex) was hung from the bottom of the skein, and the length of the skein was measured to within 1 mm and recorded as “L b ”. Crimp contraction value (percent) (before heat-setting, as described below for this test), “CC b ”, was calculated according to the formula 
           CC   b =100×( L   b   −C   b )/ L   b   
         [0034]    The 500 g weight was removed, and the skein was then hung on a rack and heat-set, with the 1.35 mg/dtex weight still in place, in an oven for 5 minutes at about 250° F. (121° C.), after which the rack and skein were removed from the oven and conditioned as above for two hours. This step is designed to simulate commercial dry heat-setting, which is one way to develop the final crimp in the bicomponent filament. The length of the skein was measured as above, and its length was recorded as “C a ”. The 500-gram weight was again hung from the skein, and the skein length was measured as above and recorded as “L a ”. The after heat-set crimp contraction value (percent), “CC a ”, was calculated according to the formula 
           CC   a =100×( L   a   −C   a ) L   a . 
         [0035]    The test was performed on five samples and the results were averaged. CC a  is reported in the Tables. This crimp measurement method is estimated to be accurate to ±2 percent absolute.  
         [0036]    The poly(trimethylene terephthalate) used in the Examples was prepared from 1,3-propanediol and dimethylterephthalate (“DMT”) in a two-vessel process using tetraisopropyl titanate catalyst, Tyzor® TPT (a registered trademark of E. I. du Pont de Nemours and Company) at 60 ppm titanium, based on polymer. Molten DMT was added to 3G and catalyst at 185° C. in a transesterification vessel, and the temperature was increased to 210° C. while methanol was removed. The resulting intermediate was transferred to a polycondensation vessel where the pressure was reduced to one millibar (10.2 kg/cm 2 ), and the temperature was increased to 255° C. When the desired melt viscosity was reached, the pressure was increased and the polymer was extruded, cooled, and cut into pellets. The pellets were further polymerized in a solid-phase polymerizer to an intrinsic viscosity of 1.03 dl/g in a tumble dryer operated at 212° C.  
         [0037]    The polystyrene used in the Examples was ‘168 MK G2’ from BASF; it was reported to be a homopolymer and to have a melt index of 1.5 g per 10 min as determined according to ASTM 1238 on 5 kg at 200° C. and a softening point of 109° C. as determined according to ASTM-D1525. It had a number-average molecular weight of 124,000 daltons as calculated according to ASTM D 5296-97.  
         [0038]    The spinneret used in the examples was a post-coalescence bicomponent spinneret having thirty-four pairs of capillaries arranged in a 1.75 inch (4.4 cm) diameter radially symmetric circle, an internal convergent angle between each pair of capillaries of 60°, a capillary diameter of 0.64 mm, and a capillary length of 4.24 mm.  
         [0039]    [0039]FIG. 1 illustrates the cross-flow quench chamber used in the Examples. Quench gas  1  entered zone  2  below spinneret face  3  through plenum  4 , past hinged baffle  18  and through screens  5  the top 2.5 cm of which were not perforated, resulting in a substantially laminar gas flow across still-molten filaments  6  which were spun from capillaries (not shown) in the spinneret. Baffle  18  was hinged at the top, and its position was adjusted to give the flow of quench gas shown in Table A, measured 5 inches (12.7 cm) from screen  5 .  
                                         TABLE A                                   Distance below   Air speed           spinneret (cm)   (mpm)                                        15   8.5           30   9.4           46   9.4           61   11.0           76   11.0           91   11.3           107   11.6           122   16.5           137   34.1           152   39.6           168   29.6                      
 
         [0040]    Spinneret face  3  was recessed above the top of zone  2  by 0.75 inch (1.9 cm) (distance “A” in FIG. 1), so that the quench gas did not blow directly onto the face of the spinneret. The quench gas, which was unheated air, continued on past the filaments and into the space surrounding the apparatus. The filament left zone  2  through filament exit  7 . Finish was applied to the filaments by finish roll  10 , and the filaments were then passed to the rolls illustrated in FIG. 2.  
         [0041]    As shown in FIG. 2, filament  6  was passed by finish roll  10 , around the pair of driven roll  11  and idler bearing  12 , and then around heated feed rolls  13 . The temperature of feed rolls  13  was about 60° C. The filament was drawn by heated draw rolls  14 , heat-treated at substantially constant length by rolls  15 , passed around unheated rolls  16  (which adjusted the yarn tension for satisfactory winding), and then to windup  17 . The speeds of the heat-treating rolls and draw rolls were substantially equal.  
         [0042]    In the Examples, the draw ratio applied was the maximum possible without generating a significant increase in the number and/or frequency of broken filaments and was typically at about 90% of break-draw. In the Tables, “Comp.” indicates a comparison sample, and “CCa” represents after-heat-set contraction in percent.  
       EXAMPLES  
     Example 1  
       [0043]    Polystyrene pellets were separately mixed with poly(ethylene terephthalate) flake (0.54 IV Crystar® 4415, a registered trademark of E. I. du Pont de Nemours and Company) and with the poly(trimethylene terephthalate) prepared as described hereinabove. The amount of polystyrene used was 2 weight percent in each case, based on total polymer. Each mixture was separately compounded using a conventional screw remelting compounder with a barrel diameter of 30 mm and a MOCA-2 screw (Werner &amp; Pfleiderrer Corp., Ramsey, N.J.). The extrusion die was ⅛ inches (3.18 mm) in diameter with a screen filter at the die entrance. A vacuum was typically applied at the extruder throat.  
         [0044]    For the mixture of polystyrene with poly(ethylene terephthalate), the first barrel section of the compounder was set at 170° C., the second section at 230° C., and the remaining ten sections at 220° C. The screw was operated at 150 revolutions per minute, and the melt temperature was 266° C. at the extrusion die.  
         [0045]    For the mixture of polystyrene with poly(trimethylene terephthalate), the first heated barrel section was set at 170° C., the second at 230° C., and the remaining ten sections at 215° C. The screw was set at 150 revolutions per minute, and the melt temperature was 261° C. at the extrusion die.  
         [0046]    In each case, the extrudant then flowed into a waterbath to solidify the mixed polymers into a monofilament. Two sets of air knives dewatered the filament, and it was passed to a cutter that sliced it into 2 mm pellets.  
       Example 2  
       [0047]    The pellets of poly(ethylene terephthalate) mixed with 2 wt % polystyrene and the pellets of poly(trimethylene terephthalate) mixed with 2 wt % polystyrene, both from Example 1, were separately dried in a vacuum oven for at least 16 hours at 120° C. The dried pellets were removed from the oven and quickly dropped into separate, nitrogen blanketed supply hoppers maintained at room temperature. The pellets were fed from the hoppers to two twin screw remelters operated at maximum temperatures of 275° C. for the mixture of polystyrene with poly(ethylene terephthalate) and 245° C. for the mixture of polystyrene with poly(trimethylene terephthalate) and then to a spin pack operated at 265° C.  
         [0048]    The mixtures were spun at a 50/50 weight ratio into a quench chamber as shown in FIG. 1. At this point the filaments of Samples 1, 2, and 3 especially, but also those of Samples 4 and 5, were judged to be partially oriented. The filaments were then passed through a roll system as shown in FIG. 2. Draw rolls  14  were heated to 90° C., and heat-treatment rolls  15  were heated to 150° C.  
         [0049]    The resulting fully-drawn filaments had tenacities in the range of 2.5 to 4.4 g/denier (2.2 to 3.9 dN/tex) and elongations-at-break in the range of 12 to 22%, with no particular relationship to spinning speed. The relationship between windup speed (“WUS”) and after-heat-set crimp values are shown in Table I and FIG. 3, in which the ‘diamonds’ represent the data from Table I. Sample 1 was spun at a withdrawal speed of about 645 m/min.  
                                                         TABLE 1                                       WUS,                   Sample   m/min   CCa, %   Draw Ratio                                        1   2515   49   3.9           2   3015   51   3.7           3   3520   48   3.5           4   4020   54   3.3           5   4520   55   3.2           6   4550   53   3.2           7   5025   40   3.0           8   5540   35   2.8           Comp. 1   5850   28   2.7                      
 
         [0050]    Data for Samples 1, 3, and 7 were average of two spins each. Examination of the data in Table I shows that high crimp values of the fully drawn filament were maintained up to windup speeds of about 5800 m/min.  
       Example 3  
       [0051]    Sample 5 was further subjected to the following tests. A skein having a denier of 27,060 was prepared and hung vertically from a stationary hook. A 50 g weight from was suspended from the bottom end of the skein, which at this point had an effective denier of 54,120. The weight was left in place for one-half minute, and the length (D) of the effectively doubled skein was determined. The 50 g weight was removed, a 4.54 kg weight was similarly hung from the skein, and the skein&#39;s length was again determined after one-half minute and labelled (B). The 4.54 kg weight was removed, and the skein was placed in a forced draft oven at 180° C. for 5 minutes, after which it was removed and allowed to cool for one minute. The skein was again hung from the hook for one-half minute with the 50 g weight suspended from its bottom end, and its length (E) was determined. Once again, the 50 g weight was removed, the 4.54 kg weight was hung from the skein, and the skein&#39;s length was determined after one-half minute and labelled (F).  
                                             The following calculations were made from the various lengths                                    % Original Bulk   =100 × [B − D]/B           % Total Bulk   =100 × [B − E]/B           % Thermal Bulk   =100 × [B − D]/D           % Thermal Shrinkage   =100 × [B − F]/B           % Net Crimp   =100 × [F − E]/F                      
 
         [0052]    Original Bulk is the percentage difference in length of a skein of yarn in the crimped and extended state and indicates crimp spontaneously developed during spinning. Total Bulk is Original Bulk plus the crimp developed by heating the yarn. Thermal Bulk is that portion of Total Bulk which is developed by heat and is not present in the original spun yarn. Thermal Shrinkage is the percent difference in length of the skein in the extended state before and after heating. Net Crimp is the percent difference in length of the skein in the extended and the crimped state, after having been heated.  
         [0053]    Sample 9 was prepared by substantially the same process as Sample 5 except that it was spun and wound up at 3990 m/min without drawing or heat-treating, in other words as a partially oriented filament. It was subjected to the same additional tests. These test results for these Samples are presented in Table II.  
                                                             TABLE II                           Original   Total   Thermal   Thermal   Net       Sample   Bulk, %   Bulk, %   Bulk, %   Shrinkage, %   Crimp, %                                5   71   81   283   30   73       9   0   72   72   44   49                  
 
         [0054]    As the data in Table II shows, Total Bulk, Net Crimp, and Thermal Bulk were all very high, the last especially so in the case of fully-drawn Sample 5. For partially oriented Sample 9, the low Original Bulk can be advantageous for downstream processing, and the very high Net Crimp, especially, is what would be expected for a filament spun at only about 2500 m/min.  
       Example 4 (Comparison)  
       [0055]    Poly(trimethylene terephthalate) and poly(ethylene terephthalate) (Crystar® 4415) were separately dried, melted, and spun into filaments substantially as described in Example 2, except that they contained no polystyrene additive, the maximum temperatures of the remelt extruders were 260° C. for the poly(ethylene terephthalate) and 250° C. for the poly(trimethylene terephthalate), draw rolls  14  (refer to FIG. 2) were heated to 120° C., and heat-treatment rolls  15  were heated to 140° C.  
         [0056]    Filament tenacities were in the range of 4.1 to 4.7 g/denier (3.6 to 4.1 dN/tex), and elongations-at-break were in the range of 11 to 25%. The relationship between windup speed (“WUS”) and after-heat-set crimp values (“CCa) are shown in Table III and FIG. 3, in which the squares represent the data from Table III.  
                                                         TABLE III                                       WUS,                   Sample   m/min   CCa, %   Draw Ratio                                        Comp. 2   2500   50   3.8           Comp. 3   2800   48   3.8           Comp. 4   3200   48   3.4           Comp. 5   3800   49   2.6           Comp. 6   4100   41   2.1           Comp. 7   4475   34   1.8           Comp. 8   4965   23   1.5                      
 
         [0057]    Data for Comparison Sample 2 were an average of two spins. Comparison of the data in Tables I and III shows that crimp values of the fully drawn filaments began to differ significantly at windup speeds of about 4100 m/min, at which speed the filaments containing polystyrene had over 30% higher crimp values than did the filaments without polystyrene additive. The difference increased as windup speeds increased. Further, at comparable crimp values, the windup speeds in Table I were demonstrated to be about 1000 m/min higher than those in Table III, a significant and unexpected advantage.