KNOW FOAM - PART 5
KNOW FOAM - PART 5
Formulating with Antifoams
by Dom Ruggeri
Back in the late eighties I was working for a large formulating house. As luck would have it, I drew a project where I was asked to develop a coolant that would be effective in heavy machining operations, yet not use chlorinated paraffin. As you may recall at that time passive extreme pressure (PEP) additives were being touted as the answer to chlorinated paraffin. However, if the formulation containing the PEP were not perfectly balanced, a precipitate would render the PEP useless. After weeks of trial and error, I finally balanced the formulation so the precipitate would not form. Only one problem remained – foam, lots of it. I remember this particular product foaming out of a lab tank and spilling all over the floor. Quite a mess. A mess that I had to clean up.
We added our standard defoamer to battle the foam, and within three days we had the precipitate problem. I submitted the product to our defoamer company asking them to develop an antifoam that would not upset the balance of the formulation. Four months passed before they managed to come up with a product. By then I had worn out three mops. We set up a meeting to discuss the results. Naturally, I was expecting a technical presentation. What we got was a sales pitch and a lesson in how to use this new product. As if that was not the worst of it, the data they presented was a shake test. This particular shake test required a sample to stay in a sealed jar for thirty days while someone to shakes the jar and fluid each week for four weeks. If the foam breaks, it is considered a pass. When I asked about the precipitate problem, they claimed they were not looking for any precipitate. I was stunned, not only didn’t they have any good data; they failed to solve my problem.
Normally that would not have bothered me but when this salesman said I should reformulate my material to use his antifoam, I wanted to choke him. I felt my stress level rising, and as we all know stress is that condition when your brain overrides your body’s desire to choke the day lights out of someone who needs it. Certainly choking this salesman would be unprofessional at best, so I questioned him at length about his shake test, and beat him with the mop handle whenever he answered evasively. I asked if he could prove that the first jar he shook was shaken at the same time interval as the last. He declined to answer. Whoop - mop handle. He would only say that the test was fair. Whoop. Once more with the mop handle before leaving to find another defoamer supplier.
Today’s metalworking fluids are expected to do so much more then ten years ago, now that foam control has become a fact of life in our industry. Yet so many formulators just grab their old standby off the shelf put in 0.3 percent, do a quick shake test and off the product goes. When the foam problems develop end-users with mop handles can get real nasty, real fast. So just how does one formulate antifoams into a coolant?
First and foremost, the antifoam must be slightly incompatible with your fluid or it will not work. Second, the antifoam should disperse and remain stable in your fluid concentrate with no float or dropout. If you see either of these two phenomena, the antifoam you selected is the wrong antifoam for your fluid. This is common knowledge, right? Wrong. It would amaze you how many people still believe that one antifoam will solve each and every foam issue they have. Of course, some defoamer companies tout this, thus perpetuating the misconception.
Many people still use static tests to evaluate antifoam performance (for example the Warring Blender test). Although this test can build up a good head of foam, the break is not representative of what the fluid will see in use. A formulator should use a test that measures foam build since that is what causes all the problems in the field. The lower the foam-build, the fewer problems one will see in use. A recirculation test will measure foam-build and if the data is used correctly, it will give a good indication of field performance.
My Friends, here is where the rubber meets the road. If a defoamer salesman tells you to mix his or her antifoam into your fluid with a high speed mixer, beat him with a mop handle and do not use that antifoam. The antifoam must be able to be mixed into your fluid using the existing mixing equipment you have in your plant. Personally, when I am testing antifoam for a customer, I use the worst mixing possible. Why? I do not know what type of equipment my customers have in their plants, therefore if my products will mix into their fluid using a magnetic stirrer or a slow anchor mixer, there will no problems mixing my antifoam into their product.
That is only the first step. As I said above, the antifoam must not float to the surface or fall to the bottom of the drum. If either of these two things occurs, you have the wrong antifoam in that product. Further, there will be a foam problem as the fluid is recirculated.
One final point: you can overdose with antifoam. If you do, you may increase and stabilize the foam. Therefore, you should choose the optimum concentration to get the antifoam performance you need. As you can see, there is a difference among antifoams and methods for using them efficiently. As always, should you have any questions please post them on the metalworking fluid forum. Thank you all for a great third year. Till next month,
*Action edits provided by the Editor.