Easy dyeable high shrinkage polyester chip combines the properties of conventional atmospheric cationic dyeable and high shrinkage PET chips. Compared with regular ones, an easy dyeable high-shrinkage PET chip is obtained by adding a third monomer with hydrophilic sulfonic acid groups, a fourth polyether monomer, and a fifth monomer of a high-shrinkage modified substance. It is the raw material of easy cationic dyeable high-shrinkage modified polyester. This specialty polyester has good dyeability and vibrant color. It can shrink to a wool-like performance in boiling water. It can be blended in high proportions with natural or other chemical fibers and achieve shrinkage through post-processing. The resulting fabric has a wool-like texture, a three-dimensional appearance, and a tactile sensation. It has become a new generation of high-simulation woolen raw materials. At the same time, it can replace acrylic fibers and has high added value, making it highly competitive in the synthetic fiber market. It has broad application prospects in blended yarns, wrinkled fabrics, home textile products, carpets, and other areas.
(60:40, Phenol: TCE @25℃)
Pre-crystallization and Drying Process of Easy Dyeable High Shrinkage Polyester Chip
The crystallization rate and crystallinity of modified cationic high-shrinkage chips are lower than those of conventional PET chips. The melting point and glass transition temperature of modified chips are also lower than that of regular PET chips. So, it is necessary to control pre-crystallization, drying temperature, and speed to prevent chip adhesion. In production, the material is first transferred to a drum at room temperature for 30 minutes, then slowly heated to 60℃, pre-crystallized and dried for 2 hours, and then heated to 130℃ for drying for 8-10 hours.
Due to the lower viscosity and melting point of modified chips, the spinning temperature should be lower than that of conventional PET chips. However, the existence of the third, fourth, and fifth monomers in modified chips weakens the activity of the macromolecular chains, increases the activation energy of the melt, and results in higher melt viscosity, poor melt flowability, and higher melt component pressure, which are highly unfavorable to spinning and forming. Therefore, the temperature range that can be adjusted during melt spinning is relatively narrow. Lower temperatures are limited by increased viscosity, while higher temperatures are limited by decomposition temperature. In actual production, the spinning temperature is typically 5-8℃ lower than that of conventional PET, ranging from 275-280℃.
Additionally, due to the higher coagulation particle content in modified chips compared to conventional PET, the pressure on the pre-filter and components increases rapidly during normal production, leading to a shorter lifespan of the components and filters. To ensure normal production and extend the lifespan of filters and components, the initial pressure of the members is appropriately reduced by approximately 2MPa. As the modified PET has a looser molecular structure compared to regular PET, which is beneficial for cooling and shaping during spinning, a gentle cooling method is adopted with an air-blowing temperature of 23℃ and a speed of 0.32m/s.
Due to the lower Tg, the drawing temperature should be appropriately reduced during the process. Additionally, higher drawing temperatures result in lower shrinkage rates. When the fiber is stretched above the glass transition temperature, the activity of the macromolecular chain segments significantly increases, leading to increased fiber crystallinity and reduced amorphous regions, resulting in decreased shrinkage. However, excessively low stretching temperatures can lead to more broken filaments and roller wrapping during stretching. In actual production, drawing is performed in a 65-67℃ warm water bath, with a drawing ratio of 2.9-3.1, to achieve optimal product quality.