Preparation method for ester and alcohol soluble type polyurethane resin used for plastic composite ink

The invention discloses a preparation method for an ester and alcohol soluble type polyurethane resin used for plastic composite ink. According to the invention, dimeric fatty acid reacts with diamine and hydroxyl-containing monoamine to produce hydroxyl-terminated polyamide with a number-average molecular weight of 400 to 2000; polyester polyol, micro-molecular dihydric alcohol and fatty alcoholpolyoxyethylene ether are added to react with diisocyanate so as to prepare polyurethane/polyamide block polymer with isocyanate groups as end groups; diamine chain extender is used for chain extension; molecular weight is controlled by using a molecular weight conditioning agent, and a diluent is added so as to prepare the ester and alcohol soluble type polyurethane resin used for plastic composite ink. The polyurethane resin prepared in the invention has a number-average molecular weight of 25000 to 60000, a solid content of 28 to 35% and a viscosity of 500 to 1500 mPa.s/25 DEG C, and has the advantages of good adhe