Method for preparing direct melt-spun high-viscosity PBAT/low-viscosity pet two-component elastic fiber and high-viscosity PBAT polymerization reactor

A method for preparing a high-viscosity PBAT/low-viscosity PET two-component elastic fiber, the two-component elastic fiber containing a high-viscosity PBAT component and a low-viscosity PET component, the viscosity of the high-viscosity PBAT component being greater than that of the low-viscosity PET component, wherein, the preparation method comprises steps of preparing a high-viscosity PBAT melt and a low-viscosity PET melt separately, and spinning the high-viscosity PBAT melt and the low-viscosity PET melt through the same parallel composite spinning assembly to obtain the two-component elastic fiber;

• the viscosity of the high-viscosity PBAT melt is greater than the viscosity of the low-viscosity PET melt;
• the step of preparing a high-viscosity PBAT melt comprises a step of sequentially passing terephthalic acid and 1,4-butanediol through a first esterification reactor for a first esterification reaction, through a second esterification reactor for a second esterification reaction, through a first prepolymerization reactor and a second prepolymerization reactor for prepolymerization reactions to give a PBAT prepolymer, a step of adding a 1,4-butylene adipate prepolymer to the second esterification reactor when carrying out the second esterification reaction, and a step of polymerizing the PBAT prepolymer in a high-viscosity PBAT polymerization reactor to obtain the high-viscosity PBAT melt, the high-viscosity PBAT polymerization reactor is a horizontal polymerization reactor, and comprises a main body containing a chamber inside, the main body comprises a low viscosity zone, a med-high viscosity zone, and a high viscosity zone disposed in sequence along the axial direction of the high-viscosity PBAT polymerization reactor, the viscosity of the PBAT melt in the low viscosity zone, the med-high viscosity zone and the high viscosity zone increases in sequence;
• the high-viscosity PBAT polymerization reactor further comprises two agitating shafts disposed in parallel in an axial direction and running through the low viscosity zone, the med-high viscosity zone and the high viscosity zone, the rotation directions of the two agitating shafts are opposite, each of the agitating shafts is provided with a plurality of discs, the circumference of the discs are circular, and the distance between the two agitating shafts is 1.05-1.10 times the radius of the discs, and the discs on the two agitating shafts partially overlap;
• the step of preparing low-viscosity PET melt comprises a step of sequentially passing terephthalic acid and ethylene glycol through a first esterification reactor and a second esterification reactor for esterification reactions, through a first prepolymerization reactor and a second prepolymerization reactor for prepolymerization reactions to give a PET prepolymer, and a step of polymerizing the PET prepolymer in a low-viscosity PET final polymerization reactor to obtain the low-viscosity PET melt.