Method for preparing lignin sulfonate dye dispersant

The invention provides a method for preparing lignin sulfonate dye dispersant. The method comprises the following step of carrying out condensation reaction on sodium lignin sulfonate, formaldehyde and a compound containing hydroxyls to generate the lignin sulfonate dye dispersant, wherein the compound containing hydroxyls is one or more of the sulfonic acid methyl naphthalene, naphthalene sulfonic acid, phenol, naphthol, benzyl alcohol and lignin, both the sodium lignin sulfonate and the compound containing hydroxyls can be subjected to the condensation reaction together with the formaldehyde to generate the lignin sulfonate with high molecular weight. The capacity of absorbing the dye molecular of the lignin sulfonate can be enhanced and the activity of the lignin sulfonate can be improved so that the lignin sulfonate has good heat-resistant stability and high-temperature dispersibility. Experiments show that the dye composite, which is obtained by singly using the lignin sulfonate dye dispersant prepared by adopting the method provided by the invention for the C. I disperse blue 79, has 5-grade stability and 5-grade high-temperature dispersibility at 150 DEG C.