抄録
A new core-sheath conjugate fiber was developed by combining poly(L-lactic acid) (PLLA) as the sheath and poly(butylene terephthalate) (PBT) as the core. The tensile strength of the conjugate fiber was found to increase with increasing melt-draw ratio and PBT composition at a constant draw ratio. SEM observation of the conjugate fiber revealed that the PBT core fiber could be pulled out from the PLLA sheath to leave smooth surfaces on both sides. DSC and WAXS data of the drawn conjugate fiber suggested that only PBT had been crystallized in the core without crystallization of PLLA in the sheath. It was therefore considered that the crystallization of PLLA was hindered by a strong stress that was applied by the crystal orientation of PBT through the interface of the two polymers in contact. The PLLA sheath of the conjugate fiber was readily removed by alkali treatment to obtain the PBT core fiber although its strength became slightly lower than that of the original conjugate fiber. This alkali treatment of the conjugate fiber can give an environmentally friendly process for the denier-decreasing treatment of polyester fiber, because the hydrolysis product, that is L-lactic acid salt, can readily be assimilated into carbon dioxide and water in environment.
