Water-based Insulating Paint The manufacturer explains that insulating varnish is a coating with outstanding electrical insulation properties. It exhibits excellent electrochemical, thermal, mechanical, and chemical performance. Most commonly available are clear varnishes and tinted paints. Insulating varnish is a specialized type of paint, serving as a crucial insulating material. Based on polymers, it can cure under specific conditions to form either an insulating film or an insulating solid.

　　Traditional solvent-based insulating paints used by motor manufacturers in China contain high levels of flammable, explosive, and toxic solvents such as benzene, ketones, and esters. After application, these paints release significant amounts of harmful substances, posing risks to human health and contributing to environmental pollution—leading to their gradual replacement by water-based insulating paints. To reduce organic solvent emissions and meet the nation’s stringent low-VOC environmental standards, many domestic institutions have been actively focusing on developing waterborne insulating paints in recent years. Insulating paints typically consist of a base resin, flame retardant, curing agent, pigment-filler, and a solvent component.

　　Water-based insulating paint refers to insulating paint that uses water as its primary solvent, and it is categorized into water-soluble and water-emulsion types. The main issues associated with water-based insulating paint include:

　　1. As the main component of water-based insulating coatings, the water-soluble polymer itself must contain a high number of polar and ionic groups—or rely on emulsification with such groups—to dissolve or disperse effectively in water. During the curing process of the insulating coating, these functional groups should be minimized to a very low level; otherwise, hydrolysis in humid environments could severely compromise the coating's insulation properties as well as its mold-resistant performance.

　　2. Water or ionic groups often cause corrosion of metals, which can damage the insulation treatment applied to metal-containing components. While the proper use of flashover-resistant technology can mitigate the corrosive effects of water-based insulating coatings on metal parts to some extent, it may also lead to a slight reduction in the insulation performance of the cured product.

　　3. It must possess adequate mechanical strength, especially at high temperatures, while still maintaining sufficient bonding integrity. Otherwise, under the influence of electromagnetic forces and mechanical stress, the windings could loosen or deform, potentially leading to accidents. However, water-soluble insulating varnishes typically struggle to achieve both excellent mechanical strength and strong adhesion.

　　The synthesis method of waterborne polyesters is fundamentally similar to that of waterborne alkyd resins, but waterborne polyesters incorporate a higher proportion of heat-resistant aromatic dicarboxylic acids, resulting in superior electrical insulation properties compared to waterborne alkyd resins. Thanks to their outstanding heat resistance and insulating performance, waterborne polyesters are now widely used as F-class and higher-grade water-based insulating coatings. Typically, during the synthesis of waterborne polyesters, hydrophilic groups are introduced into the polyester resin structure. The polyester is produced via a two-step melt-polymerization process using raw materials such as dicarboxylic acids, diols, triols, and trimellitic anhydride. After cooling, the mixture is dissolved in n-butanol to form a solution with a solid content of nearly 80%. This solution is then neutralized with DMEA and diluted with water to create a waterborne polyester specifically designed for silicon steel sheet coatings. The resulting waterborne polyester coating exhibits excellent overall film performance, making it an ideal choice for silicon steel sheet applications.