Method for synthesizing long carbon chain semi-aromatic nylon

A method for synthesizing a long carbon chain semi-aromatic nylon, wherein the method comprises:

• mixing a wet powdery nylon salt, an antioxidant, a catalyst, a surfactant, and pellets and carrying out a one-step solid state polymerization under dynamic mixing to obtain a powdery nylon,
• wherein the wet powdery nylon salt has a solvent content of 5-40% wt, and is prepared by salt-forming reaction of terephthalic acid and a long carbon chain diamine with 10-14 carbon atoms in the solvent,
• wherein the pellets promote stirring and mixing of materials and reduce sticking of materials to a wall under dynamic mixing,
• wherein the one-step solid state polymerization includes pre-solid state polymerization and post-solid state polymerization;
• in the pre-solid state polymerization, gradually increasing temperature of the system from 150-190° C. to 180-220° C., ensuring the nylon salt and the prepolymer not to be molten, and increasing the solvent vapor pressure to 1.00-2.20 MPa during the period;
• in the post-solid state polymerization, gradually reducing the system pressure to vacuum and holding for at least 1 h;
• the temperature of the post-solid state polymerization should not be lower than the termination temperature of the pre-solid state polymerization;
• wherein gradually reducing the system pressure to vacuum comprises steam releasing and vacuuming after stream releasing, and the steam releasing time is 1-3 h;
• and
• wherein the temperature of the post-solid state polymerization is increased to 200-240° C. at a rate of 3-10° C. for 0.5-1 h after steam releasing for 0.5 h.