Unsaturated Polyesters

Abstract

Unsaturated polyester resins have traditionally been manufactured in batch operations, and reactor design is an important factor. Typical polyester reactors are constructed at a length/diameter ratio of approaching unity, and are equipped with a single pitched (axial flow) turbine whose diameter is about 40 percent of that of the tank. Reactor cooling capability is the single most critical factor determining the plant's capacity, because the polymerisation is highly exothermic. Polyester reactors usually contain spiral-wound, water-filled cooling coils for this purpose. To promote a steady reaction rate and to help maintain a homogenous product, some of the reactants may be introduced continuously or in discrete additions, as the reaction proceeds. The reaction time varies between six and thirty hours, being strongly dependent upon the nature of the raw materials.