The invention relates to the field of nylon materials, and discloses a method for preparing
polyester-nylon composite fibers by melt direct
spinning. The method comprises the following steps of 1) burdening, specifically, heating and mixing
caprolactam, an end-capping
reagent, water and a catalyst to obtain a mixture; 2) ring opening; 3) pre-polycondensation, specifically, carrying out a pre-
polycondensation reaction and devolatilization; 4) final polycondensation, specifically, carrying out a final
polycondensation reaction and devolatilization; 5) devolatilizing before
spinning; and 6)
spinning, specifically, directly conveying nylon melt and
polyester melt which are devolatilized before spinning to a composite spinning
assembly, performing extruding, cooling, oiling, stretching and winding to obtain the
polyester-nylon composite fibers. By means of the method, direct spinning after nylon melt
polymerization can be achieved, slices do not need to be prepared in advance, and the content of hot water extractables and cyclic dimers in the nylon melt can be effectively controlled; and composite spinning is carried out on the nylon melt and the polyester melt to obtain the polyester-nylon composite fibers in different composite forms.