EGECat® ClearCo Series

Superior Performance in Clear Resins with EGECat® ClearCo Series Unsaturated polyester resins (DPR) are a general designation for a broad class with numerous applications today. Although their first applications were seen during the Second World War, they are now used in construction and building materials, vehicle parts in land and marine transportation, infrastructure products, energy and defence industries, textiles (buttons, accessories) and sports equipment. DPR is formed as a result of the condensation reaction of diacid(s)/anhydride(s) and glycol(s). The ratio of acid/anhydrides to glycols in the formulation varies according to the desired resin properties. The resin obtained at the end of the reaction contains unsaturated double bonds and is in soluble form in certain solvents. The curing process of the resin, which is the next step, begins with the addition of organic peroxide and is controlled by the addition of accelerators and other additives. Various additives can be added to the resin structure depending on the desired properties. Accelerators are mostly metal carboxylates. Metal carboxylates accelerate the free radical polymerization reaction starting on the unsaturated polyester resin through the decomposition of the peroxide. Cobalt, potassium and copper are metals traditionally used as catalysts in conventional applications. Other metals such as barium, calcium and manganese have been used, but the desired performance on the final resin could not be achieved with these metal carboxylates. The amount of catalyst to be added to the formulation is determined based on the desired gel time, cure time and peak exothermic temperature. The catalyst amount will vary depending on the reactivity, type of unsaturated polyester used and the application. Inhibitor type, amount and other additives are other determining parameters on performance. Cobalt plays an active role in the free radical polymerization reaction and is used to achieve the desired gel time. It is the primary (oxidative) and most important accelerator. The oxidation (2+ to 3+) and reduction (3+ to 2+) potentials for cobalt are similar, and due to this potential, cobalt is a very effective accelerator. In both cases, cobalt generates radicals, but cobalt oxidation is more dominant than the reduction reaction. For this reason, during the occurring redox reactions, Co3+ salts accumulate in the system until the polymer is cured. At the end of the curing process, the increasing Co3+ concentration can lead to discoloration of the cured resin, known as pinking. The pinking effect caused by the use of cobalt carboxylate is a major problem, especially in light-colored products such as transparent molds and artificial marble. Cobalt carboxylates are used in almost all unsaturated polyester-based composite applications with their unrivalled redox potential. This widespread application area makes pinking an even greater problem for end users. To solve this ongoing important issue, Ege Kimya developed the EGECat® ClearCo series. EGECat® ClearCo series are special cobalt complexes with reduced cobalt metal content. It consists of EGECat® ClearCo 101 and EGECat® ClearCo 102 products. EGECat® ClearCo 101 contains 2% Co and EGECat® ClearCo 102 contains 1% Co. Both complexes are designed to reduce pinking in the final product while maintaining gel time and cure properties. EGECat® ClearCo series was tested in MEK peroxide-initiated isophthalic and orthophthalic resin-based applications in comparative tests with standard cobalt octoate 6% product. Gel time, peak time and peak temperature values are shown in Table 1. No inhibitor or auxiliary catalyst was used. These results demonstrate that EGECat® ClearCo 101 and EGECat® ClearCo 102 can provide similar gel time, cure time and peak exothermic performance compared to standard cobalt carboxylate in isophthalic or orthophthalic resins. Despite their low cobalt content, EGECat® ClearCo 101 and EGECat® ClearCo 102 provide no loss in performance, while enabling the production of lighter-colored products (Figure I).   M.Sc. Bahar Taylanlı - Research and Development Assistant Specialist Ege Kimya Dr. Andrew Mason - Technical Sales Manager Ege Kimya