Glycols, saturated anhydrides, and unsaturated anhydrides are precisely weighed and loaded into the main reactor kettle under an inert nitrogen blanket.

The reaction mixture is heated to 180°C–220°C under continuous agitation, releasing water vapor as a byproduct through a fractionating column.

Vacuum pressure strips residual moisture and volatile monomers while laboratory testing verifies target acid value and viscosity.

The batch is rapidly cooled to stop polycondensation, and hydroquinone inhibitors are added to prevent premature polymer cross-linking.

The molten polyester base is transferred into a thinning tank pre-filled with styrene monomer (30–40%) under controlled low temperatures.

Specialty additives or promoters are incorporated, followed by fine mesh filtration and transfer into steel drums, IBC totes, or bulk tankers.