Method for preparing black polyester fiber by dope dyeing

The invention discloses a method for preparing a black polyester fiber by dope dyeing, which comprises the following steps: adding a black pigment carbon black into a liquid dispersion medium, sufficiently grinding, then adding a compound capable of being subjected to chemical reaction with surface groups of the carbon black, and performing grafting reaction at a certain temperature in the presence of a catalyst to obtain a uniformly dispersed black slurry; and adding the black slurry into a polyester oligomer, uniformly mixing, then performing pre-polycondensation and final polycondensation reaction to obtain a polyester molten mass, and performing direct spinning on the molten mass through a spinning manifold to obtain the black polyester fiber. According to the method disclosed by the invention, the prepared black slurry is stable at normal temperature and is favorably compatible with the polyester; the pigment is uniformly dispersed in the polymerization system; dyestuff is fixed to the fiber after the spinning formation of the molten mass, so that the product is high in color fastness; and almost no color difference exists among inter-batch and intra-batch products, thus being especially suitable for large-batch continuous production. Thus, the method disclosed by the invention is of great importance for improving the current polyester differentiation rate level in China and solving the pollution problem caused by after stain of the fiber.