Adipic Acid-Based Aliphatic Polyester Polyols

Polyester polyols used in polyester-based polyurethane flexible foam are generally synthesized through the condensation of adipic acid with diethylene glycol (or a mixture of diethylene glycol and other glycols). Small amounts of triols (such as trimethylolpropane or glycerol) can be added to replace glycols, producing mildly branched polyesters with a relative molecular weight of approximately 2000. Branching can also be achieved by using small amounts of glycerol and pentaerythritol instead of glycols. The branching degree and functionality of the product can be controlled by adjusting the type and amount of polyols. As functionality increases, the reactivity of the polyester rises, accelerating foam curing but reducing flexibility.

Polyester polyols with hydroxyl values between 45–60 mgKOH/g, synthesized from adipic acid and DEG, DEG/EG, DEG/PG (or with a small amount of TMP), typically have viscosities of 5–20 Pa·s (at 25°C). These are suitable for polyester-based polyurethane flexible foams with high elongation and tensile strength, as well as microporous polyurethane elastomers. In addition to being used for flexible polyurethane foam production, adipic acid-based polyester polyols are widely applied in manufacturing polyurethane elastomers, synthetic leather, adhesives, and coatings.

Polyethylene adipate diol (PDA) is synthesized by polycondensation of adipic acid and diethylene glycol.

1．Common Properties of Polyester Polyols:

Notes:

· Moisture content <0.03%; acid value 0.1–0.8; appearance: milky white waxy solid; APHA color <180.

High-hydroxyl-value adipic acid-based polyurethane polyols can also be used for rigid polyurethane foam production, but their dimensional stability and heat resistance are inferior to aromatic polyester polyols.