1. Raw Material Preparation
* Epichlorohydrin (ECH): A common starting material, typically derived from propylene.
* Bisphenol A (BPA): The primary hydroxyl-containing compound used in the reaction.
* Catalyst: Usually, a strong base such as sodium hydroxide (NaOH) is employed as a catalyst to promote the reaction.
* Solvent: Sometimes used to control the reaction conditions.
2.Glycidation Reaction (Epoxidation)
* In this step, epichlorohydrin reacts with bisphenol A under basic conditions (in the presence of sodium hydroxide).
3. Distillation and Purification
* The crude product obtained from the reaction is distilled to remove impurities, unreacted materials, and excess water.
* This step ensures the desired molecular weight and viscosity are achieved for the final product.
4. Control of Molecular Weight
* By adjusting the ratio of bisphenol A to epichlorohydrin, the molecular weight and properties of the unsaturated polyester resin can be controlled.
* Lower molecular weight products result in liquid unsaturated polyester resins (LER), while higher molecular weight products result in solid epoxy resins (SER).
5.End-Capping (Optional)
* Some epoxy resins undergo a process called end-capping, in which the terminal hydroxyl groups are reacted with additional epichlorohydrin to cap the ends, reducing the reactivity of the hydroxyl groups and controlling the resin’s properties.
6. Cooling and Solidification
* After the reaction and purification steps, the resin is cooled.
* Depending on the formulation, it may solidify or remain in liquid form. Solid unsaturated polyester resins are typically cooled further to form flakes or pellets for ease of handling and transportation.
7. Packaging and Storage
* Once the resin passes quality control tests, it is packed into drums, containers, or other storage units depending on its form (liquid or solid).
* The resin is stored in a controlled environment to prevent contamination or degradation before it is shipped to customers or used in further formulations.