Production Process of Saturated Polyester Resin

① Charging
The first step in commencing production, where the most critical aspects are: accurate charging and following the sequence specified by the process. The same formula with different charging sequences can affect the product. Given that polyols and polyacids have different melting points and melt at varying rates, the most suitable sequence is to divide the easily melted polyol into two portions—charged at the bottom and top of the reactor respectively—and place the polyacid in the middle of the material. During heating, this allows the polyol and polyacid to fuse into a homogeneous phase as quickly as possible, ensuring smooth progression of the reaction.

② Reaction
The synthesis of the resin involves chemical reactions such as esterification and polycondensation. The reaction process is influenced by the reaction technology, temperature, and the type of catalyst used. From a control perspective, it is essential to promptly remove the reaction water from the reactor to steer the reaction in the desired direction and avoid side reactions.

③ Intermediate Control
This step involves testing samples to determine whether the reaction has met the specified requirements. To ensure accurate testing, the solvent used for dilution after sampling must be identical in composition to the thinning solvent used in production. During sample dissolution, solvent evaporation occurs. After dissolution, the sample should be re-weighed, and any loss in weight compensated by adding dilution solvent, which improves the accuracy of the test.

④ Dilution
Once the reaction reaches its endpoint, the material is discharged into a thinning tank for dilution. Additionally, a portion of strong solvent should be added to the reactor to wash it, removing resin adhered to the inner walls. The key requirement in this step is thorough mixing.

⑤ Filter Pressing
Impurities introduced with the raw materials or generated during the reaction remain in the resin system. However, coatings made from polyester resins have fineness requirements. Therefore, filtration is used to remove impurities from the resin, ensuring the final resin product is clear and transparent.