The quality of nylon 6 POY has a great influence on DTY processing. Because there are many influencing factors, the influence of POY oil content on DTY quality is easy to be ignored.
In DTY processing, the oil content of raw filament determines the dynamic friction between filament and metal and the dynamic friction between filament and disc. When the filaments pass through the twister disc, the filaments have strong friction with each other in the transverse direction. Filaments that can't bear this kind of friction will produce fibrils and broken ends. In this case, the oil content should be adjusted to reduce the static friction between filaments. However, if static friction is too low, it will cause slippage of POY and cause twist escape when processing DTY. Increasing the winding tension can prevent the slip, but cause the increase of mesh phenomenon. Besides the DTY quality, POY oil content has a great influence on the adaptability and working environment in the post-processing process.
The oil content of POY yarn is related to the wear and the amount of "snowflakes" produced during nylon DTY processing. When the oil content of POY is low, the monomer content in "snowflake" increases, which indicates that the wear degree of filament on friction disc increases. When POY oil content is high, the oil composition in "snowflake" increases, indicating less wear. Setting proper POY oiling amount is very important for nylon POY and DTY production. With the same type of oiling agent, the formation of "snowflake" is mainly affected by the oil content of POY when the linear filament density and total density of fiber are unchanged.
When the oil content of POY is 0.45%～0.50%, DTY has the least appearance defects, the best processing stability, the longest hygienic cycle, the highest output and the best quality. This is because when the oil content is too low, the cohesive force between the individual filaments is poor, which leads to the divergence of POY, causing excessive unwinding tension of POY and the increase of breakage rate when processing DTY. On the other hand, when POY oil content is too low, the dynamic friction coefficient between the filament and the friction disc is too high, causing excessive friction and the increase of DTY fibrils. However, when the oil content is too high, the dynamic friction coefficient of the oil agent is too low, causing insufficient friction between the friction disc and the filament. In this case, filament will slip on the friction disc in the twister, causing intermittent stiff filament, namely tight filament. Moreover, a large number of "snowflakes" are produced on the friction disc due to the high friction and heat of the filaments. If these "snowflakes" are not removed in time, they will stain the surface of the friction disc, resulting in speed fluctuation of filaments when entering and leaving the twister and twist escape. There will also be a large number of defects such as tight filaments, which will affect the dyeing performance of DTY.