Abstract:
The method of this invention comprises the improvement of using an open frame skein carrier with arms to loosely hang the yarn skeins. This allows a shorter total heat-setting time; eliminates kinks, and improves bulk and bulk uniformity of the yarn.

Description:
This is a division of application Ser. No. 789,177, filed Apr. 20, 1977, and now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to an improved method to heat-set synthetic yarn by loosely hanging skeins in a conventional autoclave. 
     The prior art method and apparatus to hold skeins of yarn for heat-setting was to stack the skeins on top of one another in a carrier such as a basket or a series of trays for autoclaving. This method and apparatus produced kinky yarns, failed to develop maximum bulk on the yarn, and produced nonuniform bulk from strand to strand of yarn after heat-setting in an autoclave. See U.S. Pat. No. 3,343,380. 
     It is also known in U.S. Pat. No. 1,515,556 to loosely hang skeins of rayon for drying. 
     SUMMARY OF THE INVENTION 
     The improved method of this invention and the uniquely designed carrier allow the skeins to hang in a relaxed vertical position so that the heat can uniformly reach all portions of all skeins to impart highly desirable properties which are unattainable by other known methods for holding skeins for autoclaving. These desirable and unique yarn properties are: 
     (1) elimination of yarn kinks, 
     (2) less loss of bulk from autoclaving and 
     (3) uniform bulk development from strand to strand within the skein and from skein to skein and from autoclave load to autoclave load. 
     This method can be applied to either tumbled or nontumbled yarns. Since the treatment of the yarn is more effective with the carrier and method of this invention; the total cycle time for each autoclave load can be reduced, and the actual throughput of pounds of yarn to each autoclave can be increased. In the past, most bulked continuous filament yarn used in twist set cut pile applications has been tumbled prior to autoclaving. In recent years, the market has shown interest in the nontumbled (straight set) carpet yarn. Carpet fabrics developed around this yarn were mostly print base cut piles which have been considered to be most forgiving of yarn defects. In the last two years the fine denier soft hand silky bright look has emerged as a popular fashion in the trade. This fine denier per filament low texture yarn was found to be very sensitive to processing conditions in twist setting, tufting, and dyeing. The major area of sensitivity, i.e., cause of streaks, was found to be the twist setting operation. This invention has overcome the streaks of the prior art method due to yarn kinks, loss of bulk, or nonuniform bulk development. 
     The apparatus used with the method of this invention is a skein carrier for heat setting synthetic yarns comprising an open frame mounted on an open base, multiple arms spaced to allow skeins to pass between them from a support member mounted on the frame. This allows multiple yarn skeins to hang loosely from the arms for heat setting in an autoclave. The arms can be mounted parallel or perpendicular to the longest dimension of the autoclave vessel. The skein carrier can be mounted on any means to convey the carrier. For example, it could be mounted on a conveyor system or skids. It is preferably mounted on casters. Also preferably, the arms are cantilevered from the support member. 
     The method of this invention is for heat setting synthetic yarn loosely hung on skeins on a carrier. The method comprises 
     (a) placing the carrier in a conventional autoclave, then 
     (b) reducing pressure on the yarn to a vacuum of from about 25 to about 29 inches of mercury, then 
     (c) introducing steam to the yarn to reach temperature of about 212° F. to about 255° F. for about a period of about 3 to 7 minutes and then exhausting the steam, then 
     (d) introducing superheated steam to the yarn to reach a temperature of from about 230° F. to about 290° F. for a period of from about 3 to 7 minutes, then exhausting the steam, then 
     (e) repeating step (d), then again 
     (f) repeating step (d), for a period of from about 8 to 12 minutes, then 
     (g) holding the yarn under a vacuum of from about 20 to 28 inches of mercury for a period of from about 6 to 8 minutes, then removing the vacuum. 
     This method is applicable to nontumbled (straight set) carpet yarn when the skeins are placed on the yarn carrier directly from reeling, or to tumbled carpet yarn when the yarn skeins are placed on the yarn carrier directly after tumbling. The preferable temperature range of steps (d) to (f) is from about 240° F. to about 280° F. This preferred temperature range can be applied to either nontumbled or tumbled yarns. Also, the method can be used when heated air is substituted for steam. It is preferable to use a lower weight traveler during primary and secondary twisting of the yarn prior to forming skeins to lower the yarn tensions to less than conventional tension, preferably less than 0.2 gram per denier. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows the yarn carrier. 
     FIG. 2 shows a cross-section of an arm showing a skein hanging in place from the arm. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows the skein carrier. Open frame 1 is mounted on open base 5 which has support member 4 mounted thereon as shown. Support member 4 has arms 2 cantilevered therefrom as shown. Open base 5 can be mounted on casters 3 as a means of conveyance. 
     In FIG. 2, arm 2 is shown with yarn skein 6 hanging in position therefrom. 
     EXAMPLE 
     In order to successfully commercialize the low texture, fine denier per filament, soft hand, high luster carpet yarn products, special techniques had to be developed for twist setting. The following describes the differences between the conventional method and the improved method of this invention. The improved apparatus and method of this invention was highly successful for the heat-setting sensitive yarns. Table 1 shows the comparison between the conventional and the improved method of this process for twist-setting. Primary and secondary twisting conditions and reeling conditions are shown along with the autoclave cycle used by the conventional method and the improved method of this invention. Table II is a comparison of the conventional and improved process, including yarn characteristics. 
     
                       TABLE I______________________________________TWIST SET SPECIFICATIONS COMPARISON          CON-      THIS          VENTIONAL INVENTION______________________________________PRIMARY TWISTINGSpindle Speed, rpm            5500        5100Starting Yarn Tension, gpd            .277 to .294                        .08 to .10Ending Tension, gpd            .231 to .254                        .10 to .12Bobbin Net Weight, Lbs.            5.52        5.25SECONDARY TWISTINGSpindle Speed, rpm            5100        5100Starting Yarn Tension, gpd            .288 to .296                        .10 to .15Ending Yarn Tension, gpd            .200 to .215                        .09 to .12Bobbin Net Weight, Lbs.            6.41        5.25            (Skein Size)                        (Skein Size)REELINGYarn Skein Traverse, Inches            5.5         5.5Reel, rpm        390         400Number of Leases Per Skein            6           6AUTOCLAVE CYCLENumber of Skeins Per Basket            72 (Laid    68 (Hung            in Basket)  on Pins)1. Prevacuum to 27 Inches            4.5 Minutes 4.5 Minutes2. 1st Condition - Steam            10.0 Minutes                        5.0 Minutes and Hold (235° F.)3. Exhaust       0.6 Minute  0.6 Minute4. 1st Process - Steam            5.0 Minutes 5.0 Minutes and Hold (270° F.)5. Exhaust       1.6 Minutes 1.6 Minutes6. 2nd Process - Steam            5.0 Minutes 5.0 Minutes and Hold (270° F.)7. Exhaust       1.6 Minutes 1.6 Minutes8. 3rd Process - Steam            5.0 Minutes 10.0 Minutes and Hold (270° F.)9. Exhaust       1.6 Minutes 1.6 Minutes10. 4th Process - Steam            5.0 Minutes -- and Hold (270° F.)11. Exhaust      1.6 Minutes --12. Postvacuum (23-27 Inches)            5.0 Minutes 8.0 (Hold);                        Minutes13. Vacuum Release            --          --______________________________________ 
    
     
                                           TABLE II__________________________________________________________________________COMPARISON OF CONVENTIONAL AND IMPROVED PROCESSINCLUDING YARN CHARACTERISTICS             CONVENTIONAL                       PROCESS OFPRIMARY TWISTING  PROCESS   THIS INVENTION                                     COMMENTS__________________________________________________________________________Startup Tension, Grams/Denier             &gt;.2       &lt;.2           Lower weight traveler reduced                                     tension.SECONDARY TWISTINGStartup Tension, Grams/Denier             &gt;.2       &lt;.2           Lower weight traveler reduced                                     tension.REELINGSkein Leases      Slightly tight                       Loose         Loose leases minimize yarn                                     defects                                     (fish hooks), no restriction on                                     even                                     bulk development.AUTOCLAVE         Skeins laid in basket                       Skeins hung on special                                     Stack/laid skeins cause thick                                     and thin                       carrier       strands and low bulk                                     development which                                     result in optical streaks.                                     Hung                                     skeins allow uniform bulk                                     development                                     and thus low or no optical                                     streaks.SPECIAL TRIALA trial was run to compare skeins hung on the carrier of this inventionto skeins laid (stacked) in baskets to determine yarndifferences. All others were at what was considered to be optimum forthese fine DPF products. These trial yarns weretufted on a 3/16-inch GA tufting machine to make cut pile carpet in bandsfor direct comparison. Results of this trial areas follows:__________________________________________________________________________     CONVENTIONAL- PROCESS OF THISPROPERTIES     LAID/STACKED SKEINS                   INVENTION, HUNG SKEINS                                     COMMENTS__________________________________________________________________________Bulk      Uneven        Advantage - 1-1.5 Oz. at 32 Oz./Yd..sup.2                                     More money value with hung                                     skeins.Tips      Flared and Flat                   Round, uniform    Better tip appearance with hung                                     skeins.Uniformity     Yarn Streaks  Very uniform      Much superior and acceptable                                     uniformity                                     with hung skein and poorer and                                     unacceptable with laid/stacked                                     skeins.__________________________________________________________________________