Preparation method of black waterborne polyurethane dye

The invention discloses a preparation method of a black waterborne polyurethane dye based on black chromophores in diols. The preparation method is characterized by comprising the following steps of enabling activated hydrogen in amino groups or hydroxyls contained in molecular structures of three black dyes to react with chloroethanol to obtain three black diols; then, combining the black diols with micromolecular diols, and partially or completely substituting the micromolecular diols; and next, reacting with diisocyanate, macromolecular diols and a hydrophilic chain extender to obtain the black waterborne polyurethane dye. By using the method, other micromolecular chain extenders can be partially or completely substituted with the black diols, so that solid content of an emulsion is wide in distribution range and adjustable, and the content of the black chromophores in a molecular chain of polyurethane can be controlled as required; and meanwhile, the black chromophores enter the molecular chain of the dye in a chemical bonding way, so that the characteristics of high temperature resistance, solvent resistance and migration resistance of a macromolecular dye can be sufficiently exerted, and the dye is good in durability, high in color fastness and good in safety.