Supercritical Spray Application of Paints and Coatings

每年，美国工业喷雾应用超过500 百万加仑的油漆和其他涂料。 每 每喷一加仑油漆，平均4.5加仑 有10磅的溶剂被释放到大气中。 这些 溶剂是挥发性有机化合物（VOC）的混合物 选择它们是因为它们能够溶解涂层的 材料，并降低其粘度。 开发了一种新的工艺， 油漆和其他涂料。 它是由PI构思的， 由联合碳化物公司商业化， 其他公司 该工艺提高了 汽车、家具等喷涂涂料 商业产品和减少污染，是基于使用 超临界二氧化碳作为有机物的替代品 喷涂涂料配方中的溶剂。 其结果是一个 更均匀和改进的涂层， VOCs排放量减少80%。 虽然这一过程已投入商业使用，但仍存在一些问题 在广泛采用之前必须克服这些问题 这一技术，从而大大减少VOC 美国喷涂作业的排放量。 障碍是每一种油漆必须重新配制之前， 可以用于这个过程。 由于有数百个 不同的油漆配方，每种都有几十种不同的 这将是一项重大任务，因为 相对较少的是知道的相行为 聚合物-溶剂-超临界流体混合物， 当固相可以形成时。 因此，重新表述必须是 通过试验和错误来改变许多不同的变量。 此外，重新制定过程将单独进行， 每个油漆制造商都在偷偷地 PI计划研究热力学和流变学 聚合物-溶剂-二氧化碳混合物的性质。 的 该项目的实验部分将涉及测量， 确定这些的相图和溶液粘度 混合物。 理论部分将涉及 氢键作用的影响模型的发展 液-液相行为和模拟影响 在整个相图上的固体沉淀。 这 应促进该技术的实施， 更广泛的油漆配方，并应有助于消除 当固体形成时， 系统.

Each year, American industry spray applies more than 500 million gallons of paints and other coatings. For every gallon of paint sprayed, an average of four and one half pounds of solvents are released into the atmosphere. These solvents are mixtures of volatile organic compounds (VOCs) that are chosen for their ability to dissolve the coating's materials and to reduce their viscosity. A new process has been developed for the spray application of paints and other coatings. It was conceived by the PI and is being commercialized by the Union Carbide Corporation and other companies. The process, which improves the quality of sprayed coatings for automobiles, furniture, and other commercial products and reduces pollution, is based on the use of supercritical carbon dioxide as a replacement for organic solvents in spray-coatings' formulations. The result is a more uniform and improved coating and a reduction of the emissions of VOCs by up to 80%. Though the process is in commercial use, there are problems that must be overcome before there will be widespread adoption of this technology, and hence large reductions in VOC emissions from spray-coating operations in the U.S. The major impediment is that each paint must be reformulated before it can be used in this process. Since there are hundreds of different paint formulations, each with dozens of different components, this will be a major undertaking because relatively little is known about the phase behavior of polymer-solvent-supercritical fluid mixtures, particularly when solid phases can form. Hence, the reformulation must be done by trial and error changing many different variables. Also, the reformulation process will be done separately, and secretly, by every paint manufacturer. The PI plans to study the thermodynamic and rheological properties of polymer-solvent-carbon dioxide mixtures. The experimental part of the project will involve measurements to determine phase diagrams and solution viscosities for these mixtures. The theoretical portion will involve the development of models for the effects of hydrogen bonding on the liquid-liquid phase behavior and on modelling the effects of solids precipitation on the overall phase diagram. This should facilitate the implementation of this technology for a wider variety of paint formulations and should help eliminate process shut-downs that result when solids form in these systems.