Method for preparing cationic dyeable flame-retardant high-strength polyester fiber

A method for preparing a cationic dyeable flame-retardant high-strength polyester fiber, comprising:

• after mixing a first oligomer, a second oligomer and ethylene terephthalate and carrying out a polycondensation reaction to obtain a cationic dyeable flame-retardant polyester masterbatch, adding the cationic dyeable flame-retardant polyester masterbatch to a polyester chip according to a predetermined ratio for melt spinning, to prepare the cationic dyeable flame-retardant high-strength polyester fiber;
• wherein the first oligomer is prepared by an esterification reaction of a phosphorus flame retardant and a diol;
• the phosphorus flame retardant is more than one selected from the group consisting of 2-carboxyethylphenyl hypophosphite (CEPPA), [6-oxo-6H-dibenzo [c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid (DDP) and bis(p-carboxyphenyl)phenylphosphine oxide (BCPPO);
• the second oligomer is prepared by the esterification reaction of sodium isophthalate sulfonate and the diol;
• wherein a degree of polymerization of the first oligomer is 3-7;
• a degree of polymerization of the second oligomer is 2-6;
• and
• wherein a ratio of a sum of molar weights of the first oligomer and the second oligomer to a molar weight of the ethylene terephthalate is 3:7-6:4.