Spin-draw yarn

PTT polymer pellets must be dried to a moisture level of <30 ppm, preferably in a close-loop hot air dryer, to avoid hydrolytic degradation during melt processing. Drying is canied out widi 130°C hot air witli a dew point of <—40°C for at least 4h. Because of tire faster ciystallization rate, PTT pellets are already semicrystalline after pelletizing, and do not require pre-crystallization prior to drying as with PET. The dried polymer is extruded at 250-270 °C into bulk continuous filaments (BCFs), partially oriented yarn (POY), spin-draw yarn (SDY) and staple fiber. 

The dried polymer is extruded at 250-265° C into fibers using conventional processing machines for bulk continuous filaments (BCF), partially oriented yarn (POY), spin-draw yarn (SDY), and staple fiber. 

Nylon yarn, melt spin-draw processes for, 19 752... 

For industrial use, high-tenacity yarns, such as the tire cord, have to be drawn under conditions where low heat shrinkage, low extension, and high modulus products are produced. In fact, a tire cord is a highly specialized product, and complete integrated continuous polymerization spiiming and drawing plants (cp-spin-draw) have been developed. The process is little discussed in the open literature and the reader is directed to the patents of DuPont, Fiber Industries, and Allied Chemical Corporation (none of these companies currently exist as fiber producers). 

Fig. 4. Melt spin-draw processes for nylon yarn (a) draw-twist process, (b) conventional spinning process, and (o) coupled process.

Winders are used at the end of the spinning process, LSS or HSS, or at the end of an integrated process (spin-draw winding see Section 17.4.9), always at high speed. Winders for separate drawing processes (see Section 17.4.9) usually operate at <1000 m min f At these low speeds it is possible to wind and twist the yarn simultaneously. This is done for textile yarns. For industrial yarns twist is often applied as a separate aftertreatment. 

The production machines can be normal spin-draw winders, as for the other melt-spun fibers. But here also, compact machines have been developed, for example for bulked continuous filament yarn (BCF, for carpet) with all the process steps on one machine, at an end speed of <1000 m min h Polypropylene is small in textile applications (in sportswear) but it has a reasonable position in high-tenacity yarns, in low-temperature applications such as ropes, cables, and geotextiles. It should be added that polypropylene can be drawn to high ratios (see Section 17.7.2). This results in very good tenacities, but the helix configuration of the isotactic chain in the crystals severely limits the modulus. 

Spin-dyed BCF, a three-dimensional, crimped yarn produced partly by hot air texturing, mainly in the continuous spin-draw process (a one-step method) and partly in the undrawn yarn (UDY) with subsequent draw-texturing, to produce drawn texturized yarn (DTY). 

Spin-dyed continuous filament (CF), a fully drawn yarn (FDY), manufactured in an one-step, spin-draw process it can be converted to air-texturized yarn (ATY) in a separate process. 

The spinning speed and draw ratio are within the conventional limits, which is the reason for the introduction of the term CF, while FDY is now used for fine titer uncrimped PES and PA filament yarns, produced in a fast spin-draw process. 

Spin-drawing for CF yarn production (i.e., FDY), either used as a crimped flat yarn or further processed to a structural yam (BCF yams) in the air-intermingling process (spin-draw-texturing method). 

In parallels, efforts have been made to eliminate intermediate steps for technical yarns for BCF PP filaments, too as a result, spin-draw-winding and spin-draw-texturing processes are used for PP filament production. 

Uncrimped yarns used in textiles are mainly spun in the spin-draw process. A low or partially oriented filament yarn is being drawn completely directly after spinning in the same process between two godets. Winding speeds exceed 5000 m/min. 

Filament yarns for industrial and technical applications are mostly uncrimped yarns spun in the spin-draw process. The drawing is a two-step process with subsequent thermal fixation (four pairs of godets). 

Filament yarns for carpets are spun mostly using the BCF process, which incorporates spinning, drawing, and crimping under heat in one single process. These yarns are particularly bulky and used in more than 60% of all carpets made from... 

Application. In the past, the break strength of a synthetic yarn has averaged 34.6 lb. The first-stage draw ratio of the spinning machines has been increased. Production management wants to determine whether the break strength has changed under the new condition. 

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