With the progress of mechanical manufacturing technology and chemical processing technology, the production technology of fiber filament develops rapidly and has many kinds. According to spinning speed, it can be divided into conventional spinning process, medium spinning process and high speed spinning process. According to polyester raw materials can be divided into melt direct spinning and slice spinning. Direct spinning method is the melt in the polymerization kettle is directly sent to the spinning machine for spinning; The slice-spinning method is to melt the polyester melt made by the polycondensation process after casting belt, granulation cutting and drying before spinning, and then melt the slice into melt by using a screw extruder for spinning. According to the process flow, there are three steps, two steps and one step.

01 Conventional spinning process

Conventional spinning, also known as low speed spinning, is the earliest industrial production of a process route. A three-step process of spinning, winding, drawing, twisting and false twisting (UDY-DY-TY) is adopted. The spinning speed is 100O-1500m /min, and the drawing and twisting speed is 600-1100m /min. The false twist deformation speed is 120 ~ 160m/min, and the post-processing stretch is 3.5 ~ 4.2 times (before false twist deformation). Can be spun 33 ~ 167dtex filament.

Conventional spinning can produce both stretched and deformed silk, which is characterized by mature technology, stable operation of equipment, easy to master technology, good product quality and good dyeing uniformity. Deformable wire M(M wire is the normal dyed wire whose color absorption difference between the tested deformable wire and the standard deformable wire is within half a grade) can reach 96%. But the process is long and the production efficiency is low.

02 Medium speed spinning process

Medium - speed spinning is a two - step process. The spinning speed was 1800 ~ 2500m/min, and the semi-preoriented silk (MOY) was prepared. There are two processes for medium - speed spinning.

1. Moy-dy process

This process uses medium speed spinning and low speed drawing. Spinning speed is 1800 ~ 2500m/min, drawing and twisting speed is 800 ~ 1200m/min, can be spun 33 ~ 167dtex stretch silk, 75dtex and 50dtex are common. Its production efficiency is lower than that of high speed spinning, and its product quality is worse than that of conventional spinning.

2, MOY - DTY process

This process uses medium - speed spinning and high - speed drawing and deformation. The remaining stretch ratio of MOY is 2.1 ~ 2.4 times, and the stretch deformation speed is 400 ~ 500m/min. The deformed wire of 55 ~ 88dtex can be spun. When the tension exceeds 110dtex, two wires need to be combined to form a bobbin. The production efficiency and product quality of this process are inferior to POY-DTY process.

High speed spinning technology

The spinning speed of high speed spinning is 3000 ~ 3600m/min, and POY can be prepared. There are three processes for high speed spinning.

1. Poy-dty process

This process adopts high speed spinning and high speed drawing and deformation, which is a typical two-step process route, and is the most common process route for producing deformed silk at present.

The post-processing speed of POY is usually 400 ~ 800m/min, and it can be spun into DTY of 50 ~ 167Dtex. Its characteristics are short process, high production efficiency, capital construction investment province. POY can be stored for a long time and transported over long distances. DTY is of excellent quality.

2. Poy-ty process

This process adopts high speed spinning and low speed false twist deformation (rotor false twist method), which can spin 111 ~ 167dtex yarn. This process route is not reasonable in technology and economy.

3. Poy-dy process

This process adopts high speed spinning, low speed drawing and twisting, and can spin 55 ~ 110dtex. The drawing ratio is 1.3 ~ 1.7 times, and the general drawing and twisting machine is adopted. The performance of DY produced by this process is inferior to UDY.

04 Spinning and drawing one-step process

This process uses two processes of spinning and drawing to complete in a spinning and drawing combined machine, which is a one-step process. There are two kinds of production processes. One is the spinning speed of 900 ~ 1500m/min, the drawing speed of 3200 ~ 4000m/min, and the drawing ratio of 3.5 times, which can spin 55 ~ 165dtex. The other has a spinning speed of 2600 to 3500m/min and a drawing speed of 5100 to 5500m/min. The filament produced by this process is called FDY.

05 Other spinning processes

In addition to the above mentioned production processes, there are also high orientation filament (HOY) production processes and high crystal filament (HCY) production processes.

Highly oriented filament (HOY) is also called fully oriented filament. This process adopts one-step ultra-high speed spinning, and the spinning winding speed is 5500 ~ 6000m/min. Due to significantly increase the jet stretch, fiber orientation degree is greatly increased, but the crystallization of particles is large, amorphous area orientation degree is low, fiber dyeing performance is good, but the elongation is too large (about 40%), even if the wind speed increased to 7000 ~ 8000 m/min, elongation is still can not meet the requirement of the general use, it is in the stage of pilot production.

High crystalline wire (HCY) was prepared by one-step drawing process in high speed spinning heat pipe. In the ordinary high speed spinning process, a section of heat pipe is added before the fiber solidifies and bundles are oiled, and the filament is heated above the glass temperature (below the softening point) by hot air, so that the solidified filament is further stretched under the action of winding traction force.

Production characteristics of polyester filament

The spinning, drawing and deformation of polyester filament are carried out in each spindle. When the latter process processes the former silk ingot, although some shortcomings can be improved or made up by adjusting the process of the latter process, some shortcomings can not be made up for, but also may be amplified, such as the difference between the ingot. Therefore, reducing the difference between ingots is the key to ensure the quality of filament. With the development of spinning technology, polyester filament production has the following production characteristics.

1. High production speed

With the development of filament production technology, spinning speed is more and more high, now most of them have reached about 3500m/min. The improvement of spinning speed puts forward higher requirements for technology, equipment and operation.

2. Large volume loading capacity

The net weight of the coiled wire bobbin was increased from 3 ~ 4kg to 15kg, and that of the deformed wire bobbin was increased from 1 ~ 2kg to 5kg. With the increase of coiling capacity, new requirements are put forward for the coiling mechanism, the uniformity of the quality of the bobbin wire, and the packing and transportation of the bobbin.

3. High quality requirements for raw materials

The quality of polyester material is closely related to spinnability of filament and product quality. In addition to the required section of the intrinsic viscosity, softening point, of quality indicators, diethylene glycol content, carboxyl content, ash content and qualified condensed particles, at the same time, the appearance of the section shape, the presence of carbon black particles, the distribution of relative molecular mass, the influence of moisture content on the spinnability is big, especially the influence of moisture content of the high-speed spinning bigger, The ancient water rate of the slice is required not to exceed 30 ~ 50ppm. The quality of raw materials is required to reach the quality indicators, uniform and consistent, and the quality between batches is stable and consistent.

4. Strict process control

Filament production requires very strict technological parameters. For example, the melt temperature fluctuation does not exceed ±1℃, the wind speed difference is not more than 0.1m/s, the spinneret daily shovel surface. There are also high requirements for public works (such as water, gas, steam and electricity).

5. Total quality management is required

Filament production is a kind of multi-spindle, multi-machine assembly line work, frequent operation, labor intensive, management work quality and filament quality is very close. In order to ensure product quality, we must implement total quality management and establish quality assurance system.

6. Inspection, packaging, storage and transportation are required

In order to ensure the quality of filament yarn, the physical indexes of each batch of raw materials should be checked, the appearance defects of the winding drum should be checked one by one, and the dyeing performance of the finished silk should be sampled or completely checked. Different specifications should not be mixed in the packaging process. In addition, we should pay attention to the storage and transportation work. The storage should not be exposed to the sun or night dew, the stacked boxes should not be too high, the loading and unloading requirements should be light, and the transportation should avoid bumps as far as possible.