Low Melt Polyester for Bi-component Fiber
This paper focuses on Low Melt Polyester for single-component or bi-component low-melting polyester, which can be used for bonding fibers. But comparatively speaking, two-component fibers are more economical in low-melting polyester dosage. And the core layer is the main fiber composition, more conducive to maintaining the mechanical properties of the main fiber, so the bi-component polyester fiber has a broader market prospect.
1 Low Melt Polyester Chips Drying
As its softening point is much lower than the boiling point of water, low melt polyester is very easy to bond and very difficult to dry. As a result, we use the gradual drying method. And drying temperature can not be too high. It is generally set at 50 ~ 80 ℃ to avoid exceeding 100 ℃ or bonding.
2 Compounding Ratio
Low melting point polyester and ordinary PET generally use the sheath-core composite. Low melt polyester acts as the sheath, whose ratio determines the fiber bonding performance. If the proportion is too low, it can not reflect the characteristics of the material, and in the spinning process, it is easy to cause the skin layer to crack. And if the skin layer is too thick, it will affect the normal spinning and bring the decline of the physical and mechanical properties in fiber. According to the application requirements, the ratio generally lies in the 50:50 or so.
3 Composite Spinning Temperature
The temperature of the two polymer melt should be relatively close to the screwing extrusion temperature, which can prevent the big temperature difference between the two melts from affecting the spinnability and winding quality. The suitable spinning temperature of PET is 285 ~ 295℃. And the temperature should be appropriately lower in the composite spinning. The suitable spinning temperature for low melt point polyester is between 240 and 250℃. Considering the temperature difference between the two melts, so for the LPET screw, we should choose feedstock with a lower temperature and discharging material with a higher temperature, which is helpful for normal composite and also can avoid ring junction blocking material.
From the below picture, we can have a clear understanding of low melt polyester for bi-component fiber.