There are many kinds of polyester polyols. The main raw materials include terephthalic acid, adipic acid, succinic acid, ethylene glycol, butanediol, and more. Generating low-acid-value esterified product by esterification firstly, and then making polyester polyol product with a relatively low molecular weight by polycondensation reaction. It is mainly used in fields such as raw materials for polyester-based polyurethanes.

Two different kinds of process: Batch process and continuous process. Batch process mainly includes single-reactor system and double-reactor system, etc.; Continuous process mainly includes three-reactor process. Usually, the multifunctional reactor unit with a special structure control the acid value.