For new perspectives on effective cleaning, simply go to a trade show. What trade shows? Explore cleaning options by continuing our virtual tour of the 2019 parts2clean trade fair in Stuttgart. In the first installment of “Cleaning Perspective “(1), we discussed cyclic nucleation, laser and CO2 processes. We continue with cleaning agents and cleaning systems that use solvents, including co-solvents and hydrocarbons. We also explain how the concept of CPS can improve process consistency and minimize employee and community exposure.
One impetus for the growing diversity in cleaning processes in Europe is the increased regulatory constraints on the use of halogenated solvents, both chlorinated and brominated solvents. The parts2clean show included a range of solvents and other ways of managing solvents, some of which you may be more familiar with than others. Newer “designer” solvents such as hydrofluoro-olefins have lower global warming potential. Because most are not aggressive toward soils of interest, they are often blended with other solvents to achieve desired cleaning – primarily with trans-1,2-dichloroethylene (DCE). In fact, DCE one of the few candidates to form successful azeotropes with the designer solvents. This is important because DCE is flammable; the azeotropes, while they must be controlled, to not have a flashpoint. In the U.S., DCE is on the list to be evaluated by the EPA(2). Were DCE to be heavily restricted, there would be major challenges to industry.
It’s the process, not just the chemical!
Co-solvent cleaning or sequential solvent cleaning has been around at least since the 1980s. However, increased emphasis has been placed on process development. Cleaning equipment must be designed to control the process and to minimize carryover.
Isoparaffinic hydrocarbons have gained in popularity. They are a “cut” of molecular solvents, with carbon chains of different lengths, and the blend may vary somewhat from batch to batch. These solvents have primarily non-polar characteristics. Modified alcohols, in particular a molecule that is polar at one end and non-polar at the other, can be useful in removing residue of mixed soils. Blends of modified alcohols have been introduced in Europe and are being introduced in the US. To manage flammability and to minimize solvent emissions, isoparafiinic hydrocarbons and modified alcohols are best used in enclosed, contained systems with appropriate engineering controls.
Traditional, more aggressive halogenated solvents may be the best option for complex, water-sensitive product and for removing very adherent soils. These can also be managed with contained solvent systems. A number of providers of contained solvent systems offered cleaning equipment at parts2clean.
There is also growing interest in CPS or Chemical Product Services. CPS is not necessarily a product, although it can involve specific chemical handling and transfer equipment. It is a term related to product support and to product stewardship. Properly accomplished, CPS can be used to minimize chemical exposure and to maximize process control. With CPS and with cleaning process development, the important thing for you as a manufacturer is to understand and evaluate what is being offered. In other words, and as responsible suppliers of cleaning agents and cleaning equipment would be quick to tell you, CPS is not a substitute for rational behavior.
Critical cleaning is (or ought to be) a value-added process. The processes we saw at parts2clean typically involve a substantial capital investment. In our experience, we find that, with well-chosen processes, the total cost of ownership can be affordable; the initial investment can be offset by lower ongoing process costs as well as having more consistent process control and higher yield. If a cleaning step is not value-added, eliminate it (unless you have some sort of arbitrary customer requirement). Find the true critical cleaning steps. Step back, look at those steps from the perspective of process improvement. You will become more productive, more profitable. Are you not sure about a new cleaning process? Give us a call; send us an email – we’ll discuss it with you!