Prepn process and apparatus of polyurethane fiber

The present invention relates to preparation process and apparatus of polyurethane fiber. The preparation process includes: mixing PTMEG, MDI and 1,3-propylene glycol in a prepolymerizing reactor; and pre-polymerization in the prepolymerizing reactor separated into two sections, including a front main section to the material to the reaction temperature of 70-75 deg.c via 80-90 deg.c hot water ledinto its jacket and a back section to cool and stabilize the prepolymer via 5 deg.c cooling water led into its jacket. The solvent used is pyrrolidone, which can makes the chain-expanding reaction smooth, eliminate gel and raise the concentration of spinning liquid and the chain expanding agent used is benzene diamine and dibutylamine to raise the strength and dyeing performance of the fiber.