The invention relates to
polyester FDY
fiber and a preparation method thereof. The preparation method comprises: metering a modified
polyester melt, extruding, cooling, oiling, drawing, carrying out
heat setting, and winding to prepare the
polyester FDY
fiber, wherein the unchanged longitudinal height is maintained during the cooling, the cross section area of the
slow cooling chamber is increasedwhile the plate surface temperature of the
spinning plate is maintained by using the
thermal insulation method. According to the present invention, the material of the
fiber is the modified polyester, the molecular chain of the modified polyester comprises a
terephthalic acid chain segment, an
ethylene glycol
chain segment and a
diol chain segment having the branched chain, the structure formulaof the
diol chain segment having the branched chain is defined in the specification, R1 and R2 are respectively and independently selected from
straight chain alkylidene with a
carbon atom number of 1-3, R3 is selected from
alkyl with a
carbon atom number of 1-5, and R4 is selected from
alkyl with a
carbon atom number of 2-5; the
chromatic aberration [
delta]E of the prepared fiber is less than 0.200; and the preparation process is simple and reasonable, and the prepared fiber has excellent performance.