As I have said before on this blog, I am not a chemist. Whatever I say about chemistry on the blog is expressed in layman’s terms and is based on practical experience and not on any deep understanding I have of the properties of chemicals. The usefulness of any information provided here applies only to industrial cleaning!
Hydrocarbons including oil, grease, wax and the like are common contaminants that are targets of industrial cleaning. In some cases, hydrocarbons may be the major contaminant while in others they are just incidental contaminants which, although they must be dealt with, are not the real target of the cleaning process. This blog deals with how the nature and amount of hydrocarbon contamination may drive the selection of a cleaning chemistry. Solvents, for the most part, remove hydrocarbons through a process of dissolution. Hydrocarbons are disbursed in the solvent and are rinsed away by more clean solvent until the desired degree of cleanliness is achieved. Solvents, although effective cleaners, are not always the practical answer in industrial cleaning. In general, they are relatively expensive and difficult to handle. In this blog, we will discuss the more commonly used aqueous-based chemistries.
There are two basic ways that aqueous cleaning chemistries interact with hydrocarbons – they either displace them or emulsify them. Chemistries that displace oil are commonly called oil “splitters” while those that emulsify oil are called oil “emulsifiers.” Let’s first look at chemistries that “split” oil.
Splitting Chemistry –
Chemistries that split oil commonly contain ingredients (surface active agents) which have a stronger affinity to bond to the surface being cleaned than that of the hydrocarbon material (usually oil) being removed. In effect, the chemistry sneaks under the oil and bonds to the surface being cleaned thereby displacing the oil as shown in the following illustration.
Additional information about the attractions described above can be found in the blogs – What is Surface Tension and Is It Clean? – Oil and Hydrophobic Films – Contact Angle and Beyond.
In most cases, the properties of oil that is removed from a surface in this way do not change. It is still basically the same oil but existing in an unfriendly environment where it does not have a “home.” Being (in most cases) lighter than the cleaning solution, the oil floats to the surface. It is an important consideration that most “splitting” chemistries are not consumed in the process of removing oil and, therefore, do not require frequent replenishment or replacement. Another important consideration is that the oil, once removed, can, potentially, be collected and re-used. In a perfect situation there would never be a need to replace the cleaning chemistry or the oil in a manufacturing operation. It is interesting to note that this goal has nearly been achieved in a few cases!
Of course, once oil has been “split” from a surface the next step is to collect and dispose of (or re-use) it. There are several ways in which this can be accomplished both manually and in an automated way. The next blog will discuss chemistries that emulsify oil and then we’ll talk about how to collect oil that has been either split or emulsified.
– FJF –