1.Conventional Spinning Process
Conventional spinning, also known as low-speed spinning, is one of the earliest industrialized production processes. It employs a three-step process route that includes spinning, winding, stretching, twisting, and false-twist texturing (UDY-DY-TY). The spinning speed ranges from 1000 to 1500 m/min, with the stretching and twisting speed between 600 to 1100 m/min. The false-twist texturing speed is 120 to 160 m/min, and the post-processing stretch ratio is between 3.5 to 4.2 times (before false-twist texturing processing). It can produce filaments ranging from 33 to 167 dtex.
Conventional spinning is capable of producing both stretched yarn and textured yarn. Its characteristics include mature technology, stable equipment operation, easy technical mastery, good product quality, and uniform dyeing properties. The quality of textured yarn M (M yarn refers to the normal dyed yarn whose color absorption difference with the standard textured yarn is within half a grade) can reach 96%. However, the process flow is long, and the production efficiency is low.
2.Medium-Speed Spinning Process
Medium-Speed Spinning is a two-step process. The spinning speed ranges from 1800 to 2500 m/min, producing partially pre-oriented yarn (MOY). There are two process routes for medium-speed spinning:
MOY-DY Process
This process uses medium-speed spinning and low-speed stretching. The spinning speed is between 1800 to 2500 m/min, with the stretching and twisting speed at 800 to 1200 m/min. It can produce stretched yarn in the range of 33 to 167 dtex, with common deniers being 75 dtex and 50 dtex. Its production efficiency is lower than that of high-speed spinning, and the product quality is inferior to conventional spinning.
MOY-DTY Process
This process employs medium-speed spinning and high-speed drawing and texturing. The remaining stretch ratio for MOY is between 2.1 to 2.4 times, with the drawing and texturing speed at 400 to 500 m/min. It can produce textured yarn in the range of 55 to 88 dtex. When exceeding 110 dtex, it is necessary to ply two yarn strands together into one package. The efficiency of this process is higher than that of the MOY-DY process, and the product quality is better.
3.High-Speed Spinning Process
High-speed spinning operates at speeds of 3000 to 3600 m/min, producing pre-oriented yarn (POY). There are three process routes for high-speed spinning:
POY-DTY Process
This process involves high-speed spinning and high-speed drawing and texturing, representing a typical two-step process route and currently the most common method for producing textured yarn. The post-processing speed for POY is typically 400 to 800 m/min, which can produce textured yarn (DTY) in the range of 50 to 167 dtex. Its features include a short process flow, high production efficiency, and reduced capital investment. POY can be stored for long periods and transported over long distances; DTY has excellent quality.
POY-TY Process
This process uses high-speed spinning and low-speed false-twist texturing (rotor false-twist method), capable of producing textured yarn in the range of 111 to 167 dtex. This process route is technically and economically unsound.
POY-DY Process
This process employs high-speed spinning and low-speed stretching and twisting, suitable for producing stretched yarn in the range of 55 to 110 dtex. The stretch ratio is between 1.3 to 1.7 times, using standard stretching and twisting machines. The DY produced by this process does not perform as well as UDY.
4.Spinning and Stretching One-Step Process
This process combines the spinning and stretching operations into a single step on a spinning-stretching integrated machine, following a one-step process route. There are two production methods: one with a spinning speed of 900 to 1500 m/min and a stretching speed of 3200 to 4000 m/min, achieving a stretch ratio of 3.5 times, capable of producing stretched yarn in the range of 55 to 165 dtex; the other method has a spinning speed of 2600 to 3500 m/min and a stretching speed of 5100 to 5500 m/min. The filament produced by this process is known as FDY (Fully Drawn Yarn).
5.Other Spinning Processes
In addition to the above-mentioned processes, there are also high-orientation yarn (HOY) production processes and high-crystallinity yarn (HCY) production proces ses for polyester filaments.
High-Orientation Yarn (HOY), also known as fully-oriented yarn, utilizes a one-step ultra-high-speed spinning process with a winding speed of 5500 to 6000 m/min. Due to the significant increase in spinneret stretch, the orientation of the fibers is greatly enhanced. However, the crystalline particles are larger, and the orientation of the amorphous regions is relatively low, which results in better dyeing properties of the fibers. Yet, the elongation is too high (around 40%), and even when the winding speed is increased to 7000 to 8000 m/min, the elongation still does not meet the general requirements for apparel use, and it is currently in an experimental production phase.
High-Crystallinity Yarn (HCY) is produced using a high-speed spinning process with a hot tube stretch in one step. In the conventional high-speed spinning process, before the fiber coagulation and oil application, a hot tube segment is added where hot air heats the yarn above the glass transition temperature (but below the softening point), allowing the coagulated yarn to be further stretched under the traction of the winding.