Core Spinning

TM

A FEELING THAT LASTS

CORE SPINNING

By

CORE SPINNING

This brochure describes general practices for producing core spun yarns with DOW XLATM elastic fiber.

INTRODUCTION

SHIPPING AND STORAGE

ASTM Method D 123 defines a core spun yarn as “a compound structure in which a filament or strands serves as an axis around which a cover of either loose fiber or yarn is wound.” When the axis fiber is elastomeric, the yarn is considered a soft core yarn.

DOW XLA elastic fiber is supplied on tubes, approximately 146 mm in diameter with 58 mm wide cores. These tubes will fit the gauge of most spinning frame core creels. For those creels with a wider gauge (e.g., 87 mm), it is recommended that spacers be used between spools to help keep them in position.

To produce elastic soft core spun yarns, the elastic core is drafted or stretched before wrapping with the companion fiber. When the composite yarn is in a relaxed state, the elastic core can retract or recover, imparting stretch in fabrics in which it is incorporated.

DOW XLA fiber performs best in core spinning when the storage guidelines outlined below are followed: 1. Apply “first in – first out” stock rotation.

In principle, any staple spinning system can be used to produce soft core yarns. Recommendations in this brochure are specific to cotton and polyester/cotton blend yarns spun on short staple ring systems. Please contact a Dow representative for recommendations with respect to other spinning systems and yarn blends.

2. Store fiber in sealed boxes below 30°C (86°F).

WHAT IS DOW XLATM FIBER?

INFORMATION INSIDE THE CONE

DOW XLA fiber is an olefin-based elastic fiber from The Dow Chemical Company. Due to its chemical and thermal properties, DOW XLA fiber is singularly suited to deliver a soft hand, comfort stretch, dimensional stability, and durable elasticity to stretch fabrics.

Inside of the cone is a sticker that contains 3 lines of letters and numbers. Each line contains valuable information that is explained below:

3. Spools should be used within 12 months of production date. (See explanation for the sticker inside the cone outlined in the next section.) 4. Partially used spools should be returned to boxes, sealed, and stored as noted above.

1. Line one is a 5-character code consisting of 2 letters, then 2 numbers, followed by 1 letter. First letter is the year. S = 2004, T = 2005, U = 2006, V = 2007, W = 2008, etc. Second letter is the month. A = Jan, B = Feb, C = Mar, D = Apr … L = Dec Characters 3 and 4 are numbers that represent the day of the month, range is 01 to 31. The last letter is the production site. S = Tarragona, Spain. 2. Line two is a series of 3 numbers, each separated by a blank space. This helps us determine the production line and position used to manufacture that spool of fiber. 3. Line three identifies the fiber denier of the spool.

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CORE SPINNING

SPINNING Frame parameters

Drafts

The following spinning frame parameters are recommended for use in the production of core spun yarns containing DOW XLA elastic fiber. If your equipment does not meet these recommended parameters, please contact a Dow representative to discuss procedures for your equipment.

The draft of the core determines the power of the yarn and also affects the coverage (how uniformly and tightly the sheath covers the core). Due to the unique load-elongation response of DOW XLA elastic fiber, higher drafts are recommended, as compared to spandex core spun yarns. Figure 2 (below) shows recommended drafts based on denier. The winding denier of DOW XLA fiber on the spools is the same as the stated denier. There is no pre-drafting during fiber production. Therefore recommended drafts are machine drafts with no need for pre-draft calculations.

Gauge The distance between the spindle center lines is the gauge of the spin frame. To reduce the occurrence of sheath damage due to balloon contact with separators, 75 mm and 82.5 mm gauges are recommended for fine and coarse count core spun yarns, respectively.

Spin Geometry/Spin Ratios Proper spin geometry is important to control spinning tension and reduce the occurrence of break backs and core breaks during spinning. Generally, it is better to use a large bobbin diameter with a small ring diameter – specifically a ring diameter to bobbin diameter ratio of 2:1. A maximum bobbin length to ring diameter ratio of 5:1 should be used to ensure that the angle of pull is greater than 30 degrees. Longer bobbins relative to ring diameter lead to higher tensions. This rule should be followed for cotton, synthetic, and blended yarns to help prevent core breaks, scuffing of the fibers, and dyeing problems. Figure 1 (page 3).

Travelers Selection of traveler weight is critical to control spinning tensions and core coverage. Proper traveler weight selection requires some experimentation to ensure balloon stability and good bobbin build and density. The lower retractive force of DOW XLA fiber dictates lighter traveler weights than those typically used in spinning soft core yarns. Traveler weights one to two numbers lighter than those used with spandex are a good starting point for selecting travelers for core spinning with DOW XLA fiber. Please see Figure 3 (page 3) for a visual reference depicting optimal yarn tension in core-spinning with DOW XLA fiber. For additional assistance in selecting traveler profiles and weights, please contact a Dow representative.

Top Cot Hardness and Load Softer front rolls with lower nip pressures are recommended to reduce probability of core damage in the front nip. Therefore, the lowest Shore A front rool and load spring feasible without jeopardizing yarn quality should be installed. Front rolls with Shore A hardness of 65 to 72 have been used with success, along with roll loads of around 30 pounds of force (lbf).

Spinning Speed Selecting spindle speeds is a function of frame geometry, ring diameter, twist multiple, traveler type, and yarn count. For example, finer yarns spun on smaller rings using lighter travelers can run at higher spindle speeds. Conversely, lower spindle speeds are required for coarser yarns spun on larger rings using heavier travelers. As a general rule, traveler speeds below 23 m/sec are recommended for core spun yarns containing DOW XLA fiber. The corresponding spindle speeds for different ring diameters are presented in Figure 4 (page 4). Before spinning at higher than recommended speeds, please consult a Dow representative to discuss spinning parameters.

Filament Centering As with all core-spun yarns, care must be taken to maintain the core filament in the center of the sheath fibers. Alignment should be set accurately at the start of spinning and checked periodically. The DOW XLA fiber should be centered to the sliver. The V-guide used to position the sliver should have little to no side-to-side movement which may effect the centering of the core fiber.

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CORE SPINNING

Ne Nm

7 12

10 17

3

14 24

20 34

24 40

30 50

40 70

CORE SPINNING

50 85

60 100

80 135

Start Up Procedure for Core Spinning For quality yarn production, the following start up procedure is recommended:

10. Run approximately 100 meters of yarn, collecting 4 bobbins to verify that yarn count, twist level, and core draft are correct. 11. Begin core spinning.

1. Verify that all rolls, v-guide, and creels are free of any fiber, roving or yarn wraps. Any laps that occur during spinning should be removed prior to piece up of the broken end. 2. Make sure the roving traverse is disengaged. 3. Set the ring rail movement for a fast up stroke and slow down stroke. This motion is preferred for lower ends down rate, better balloon stability, and longer traveler and ring life. 4. Insert the appropriate gears for the target yarn count, twist, and core draft. 5. Install the lowest Shore A front roll and load spring feasible without jeopardizing yarn quality.

12. After 3 to 4 hours of production, select a minimum of 5 bobbins from each side of the frame and test for yarn count, evenness, and physical properties. 13. Doff and discard the start up bobbins to eliminate inclusion of piece up yarn in cones.

Conditioning/Steaming For most applications of core-spun yarns with DOW XLA fiber, yarn steaming is not recommended or required. If necessary for acceptable weaving performance, core-spun yarns containing DOW XLA fiber can be steamed. Steaming will stabilize the core-spun yarn and temporarily reduce the retractive force of the DOW XLA fiber.

6. Install the recommended traveler. 1) Optimum steaming temperature for greige yarns with DOW XLA fiber is 50-60°C.

7. Creel in the appropriate roving. 8. Creel in the core. Spools should be handled with care to avoid scuffing, denting, or bruising. Spools that have been bumped or dropped should be checked for damage prior to installation in the creel. 9. Piece up the yarn and verify core position. The v-guide or roving should be adjusted so that the core is centered in the middle of the roving ribbon.

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2) Optimum steaming temperature for yarns with DOW XLA fiber for yarn dyeing is 85-90°C. Steaming yarns containing DOW XLA fiber does not lower the shrinkage potential of the yarns, but does lower the retractive force of the yarn. This means that steamed yarn may not give the desired stretch result in tight fabric constructions, coarse yarns, or heavy fabrics. Fabric construction, denier selection for the DOW XLA fiber, and finishing processes may need to be modified to achieve desired stretch if high-temperature yarn steaming (or yarn dyeing) is required.

CORE SPINNING

WINDING Key Parameters

Winding Tension

A defect unique to soft core yarns is the short core void, characterized by small, broken sections of elastic fiber along the length of the yarn. Appropriate winding conditions are key to preventing this type of defect. Specific winding parameters of importance are cradle pressure, winding speed (and program), and winding tension.

Yarn tension during winding affects package density and yarn quality. As a general rule, tension disks should be adjusted so that the average tension during winding is approximately 15% of the yarn’s breaking strength. Winders with auto-tension programs further reduce the probability of core breakage by adjusting disk tension and/or winding speed when yarn tension exceeds a predetermined level. Check with the equipment supplier regarding use of this option.

Cradle Pressure

This section covers general comments on winding parameters. For winding conditions for a specific make and model winder, please consult a Dow representative.

Typically, cradle pressure is controlled using a counter balance, where increasing pneumatic pressure lifts the cradle and reduces drum/cone contact pressure. Cradle pressure also affects the package density – lower cradle pressures produce softer, less dense cones. It is important to find the optimum pneumatic pressure to produce firm cones without causing core breakage. Some experimentation may be required to identify this optimum balance. In comparison to spandex-based products, core spun yarns made with DOW XLA elastic fiber should be wound at lower cradle pressures. As a starting point, lower the cradle pressure by setting the pneumatic pressure in the range of 3.0 - 3.5 bar.

Package Size Four to 5 pound packages can be wound with core spun XLA™ yarns that are to be knit or woven in greigh form and then dyed once in fabric. To ensure uniform dying of package dyed yarns the core spun XLA™ yarns should be wound with minimal tension and wound into much smaller packages, typically 3/4 to 1.5 pounds.

Start Up Procedure for Winding 1. Verify that machine parameters are set to recommended levels. 2. Make sure all winder surfaces are clear of dust, yarn, or core fragments.

Winding Speed Depending on yarn count and equipment limitations, it is feasible to wind core spun yarns made with DOW XLA elastic fiber at speeds averaging from 750 meters/minute to 1000 meters/minute. Critical to speed selection are yarn count, yarn strength, and speed program options. Yarns finer than 30/1 Ne and yarns containing 20 and 40 denier DOW XLA core yarns may require winding speeds as low as 700 meters/minute. Preferred programs are variable speed options – those that allow winding speed to decrease as the bottom portion of the bobbin is approached (where the tension is highest). By varying the speed, yarn quality can be improved, production increased, and piece bobbins due to yarn breaks reduced. A reasonable program for core spun yarns containing DOW XLA elastic fiber begins speed reduction when 70% of the yarn length on the bobbin has been wound, with a final winding speed 20% less than the initial winding speed.

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3. Install specified cone. 4. Bobbins will feed to each position (automatically or by hand). 5. Start winding operation. 6. Check for core fragments, especially on landing behind cone. 7. If core fragments are found, stop production and re-check winder settings. 8. Clean winder surfaces prior to restart.

CORE SPINNING

TM

A FEELING THAT LASTS

For more information about XLA fiber by DOW: www.dowxla.com or call: Europe: +32 3 450 22 40 US and Canada: +1 800 441 43 69 Mexico: +95 800 441 43 69 Asia Pacific: +603 7 958 33 92

NOTICE: No freedom from any patent owned by Dow or others is to be inferred. Because use conditions and equipment may differ from one location or application to another and may change with time, Customer is responsible for determining whether products and the information in this document are appropriate for Customer's use and intended applications. Dow assumes no obligation or liability for the information in this document. NO WARRANTIES ARE GIVEN; ALL IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE ARE EXPRESSLY EXCLUDED. TMTrademark

of The Dow Chemical Company (“DOW”) or an affiliated company of Dow

CORE SPINNING Form No. 724-10701-1006 EST