How to control the fiber fineness of Polyester DTY during production?

In the production process of Polyester DTY (polyester stretched textured yarn), the control of fiber fineness is crucial, which can be started from raw material selection, spinning process parameter adjustment, equipment maintenance and other aspects, as follows:

Raw material selection
Polyester chip characteristics: Select polyester chips with stable intrinsic viscosity. The intrinsic viscosity is generally controlled between 0.64-0.68dL/g, which directly affects the fluidity and spinning performance of the melt, and then affects the fiber fineness. If the intrinsic viscosity is too high, the melt viscosity is large, and the spun fiber is coarse; otherwise, it is thin. At the same time, it is necessary to ensure that the moisture content of the chips is below 0.4% to avoid the influence of moisture on the viscosity of the melt and the stability of spinning, resulting in fluctuations in fiber fineness.

Spinning process control
Spinning temperature: Usually the spinning temperature is preferably 280-290℃. If the temperature is too high, the melt viscosity decreases, the fluidity increases, and the fiber becomes thinner; if the temperature is too low, the melt fluidity is poor, and the fiber becomes thicker. In production, the spinning temperature should be precisely controlled according to the characteristics of polyester chips and equipment conditions, and the fluctuation range should be controlled within ±1℃.
Spinning speed: The spinning speed is inversely proportional to the fiber fineness. Generally, the conventional spinning speed is 1000-1500m/min. When fine denier fibers need to be produced, the spinning speed can be appropriately increased to 2000-3000m/min. However, if the spinning speed is too high, hair and broken ends may occur, affecting the fiber quality.
Metering pump speed: The metering pump is a key device for accurately controlling the melt flow rate. According to the required fiber fineness, the extrusion amount of polyester melt is controlled by adjusting the metering pump speed. For example, in the production of 1.5D Polyester DTY, the metering pump speed is usually set at 30-50r/min. The faster the speed, the greater the extrusion amount and the thicker the fiber, and vice versa. The metering pump speed needs to be accurately adjusted according to the actual production situation to ensure the stability of fiber fineness.

Control of stretching deformation process
Stretching multiple: stretching multiple is an important factor affecting fiber fineness. Generally speaking, the stretching multiple is between 3-5 times. The larger the stretching multiple, the thinner the fiber is stretched. However, if the stretching multiple is too high, the fiber is easy to break and the strength decreases; if the stretching multiple is too low, the fiber fineness does not meet the requirements and feels hard.
Hot box temperature: The hot box temperature during the stretching process affects the softness of the fiber and the mobility of the molecular chain. The temperature of the first hot box is generally controlled at 180-220℃, and the temperature of the second hot box is slightly lower than that of the first hot box, at 160-200℃. If the temperature is too high, the fiber will be stretched too thin due to excessive softening, and yellowing and other problems may occur; if the temperature is too low, the fiber is difficult to stretch and the fineness is uneven.

Equipment maintenance and management
Spinneret maintenance: The hole type and aperture of the spinneret directly determine the initial shape and fineness of the fiber. Regularly check the hole state of the spinneret to prevent blockage, wear and other conditions. For spinnerets that have been used for a long time and have serious wear and tear on the holes, they should be replaced in time to ensure the consistency of fiber fineness.
Maintenance of the wire guide and roller: The surface state and rotation accuracy of the wire guide and roller have an important impact on the stretching and fineness control of the fiber. Clean the wire guide and roller regularly to prevent the surface from hanging wire and material accumulation, and check whether they rotate flexibly. If there is wear or reduced accuracy, repair or replace them in time to avoid fluctuations in fiber fineness due to uneven friction.

Polyester DTY Purple ZP0471-ZP0566 306