Developing a coating with improved dirt pickup resistance continues to be an important goal in the coatings industry. Reasons for this include growth in “softer” elastomeric wall and roof coatings; demand for low-VOC formulations, which traditionally result in tackier coatings due to reduced glass transition temperatures (Tgs); and the planned construction of high-rise commercial buildings, most notably in Asia, which is driving the need for coatings that are easier to clean and maintain.
One approach to improving dirt pickup resistance has been to create a harder finish by raising the Tg of the coating. There are, however, downsides to this approach. First, it is nonviable in elastomeric applications, such as elastomeric roof coatings that require elongation and flexibility, since the increased Tg can decrease the flexibility of the coating. Such a decrease in flexibility can lead to the formation of cracks in the coating. Second, increasing the Tg of a coating can require the use of coalescing solvents, which typically have a high VOC content. The increased VOC is in direct opposition to the need to decrease VOCs in coatings due to government regulations.