The invention discloses a method for preparing semi-aromatic nylon and belongs to the technical field of macromolecular
material synthesis. The method comprises the following steps: (1) uniformly mixing aliphatic
diamine and water of which the weight is two to ten times that of the aliphatic
diamine, heating the mixture to the temperature of between 50 and 90 DEG C, adding aromatic diacid into the mixture with stirring till a pH value of the solution reaches 7.0-7.7, continuously stirring for 1 to 5 hours, cooling the solution to
room temperature, continuously stirring the solution for 1 to 5 hours again, and filtering and
drying to obtain nylon salt for later use; and (2) adding the prepared nylon salt and a
solvent to a
polymerization kettle in a certain mixture ratio (0.5 to 3.0 g / mL), raising the temperature to between 190 and 230 DEG C under the protection of
inert gas, keeping the pressure in the kettle between 2.0 and 3.0 MPa, discharging gas after 1 to 5 hours to make the pressure in the kettle reduced to normal pressure within 1 to 5 hours, raising the temperature to between 210 and 270 DEG C, and continuing to react for 1 to 5 hours, and discharging to obtain a powdery semi-aromatic nylon product. The method has mild reaction condition and low
energy consumption; the product is easy to mold and
machine; and the method solves the difficult problem of difficult discharging of the semi-aromatic nylon, and is applicable to industrialized production.