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Selective What?

by Dom Ruggeri

July 2003:

When I am in the mood I occasionally think back to how long I have been in this crazy business.  Some years back a green kid walked out of school and found out he didn’t know anything.  Now some twenty years later I find that I still don’t know anything.  For example, back in the late eighties to mid-nineties I was working at a major formulating house.  A customer had been buying a modest soluble oil for many years when the powers that be decided to switch them over to one of the newer, higher priced soluble products. 

At the time this seemed like a very good idea, but like most ideas it is only good till it’s implementation.  After about 6 weeks in the system, problems began to emerge such as tool life going to pot, part finish not in specification, scrap rate going up; all the signs of a system that is not well maintained.  Then two weeks later we heard the word that scares everyone in the metalworking industry the most: "dermatitis."  If you truly want to bring fear into a Coolant salesman’s heart, just say "dermatitis."  Never before was a team of technical people dispatched so quickly as when this particular customer reported the dermatitis problem. 

Of course we ran the standard battery of tests.  What we found was quite intriguing.  Normally a diluted coolant will begin with a pH of say 9.5.  As the coolant recirculates in the system, the pH of the coolant will begin to drop.  Within, say a day or two, the pH will level off at about 8.5 to 9.0 depending on how much reserve alkalinity is present.  As the coolant recirculated, the pH actually rose, hence the dermatitis problem.  We began to pass out various barrier creams to the machine operators on the shop floor, a band-aid yes, but we needed time to ascertain what was causing the problem.

As with any investigation we only had so much time, and a customer is only so patient, so we checked everything from the make up coolant to the concentration tests.  Nothing seemed amiss, until we noticed that there was a cream layer on the emulsion.   We quickly ran a few tests and found that the lubricant package was coming out of the emulsion as it was recirculated, and was also being drug out with the parts, while the water soluble moieties were remaining in the water phase.  This would account for the pH going up and all the other ills of this particular system.

How do we solve this mess? Back in the lab we concocted a base material consisting of extra emulsifier and the lubricant package.  Our reasoning was that this base would pull in the cream layer and provide the extra emulsification giving yielding a stable coolant.  Why this approach?  Economics and customer relations.  The customer had 5 tote bins of the original soluble oil in stock, so we had to work with what we had.

Emulsifier Bases are versatile compounds that are a mixture of emulsifiers, fatty acids, surfactants, and in some cases sulfonate.  The principal here is that all the formulator needs to do is put together the additive package be it extreme pressure, corrosion, and of course oil add emulsifier base and instant product.  Many small formulating houses rely on these materials, however, the larger ones will formulate their own bases. 

Now this may sound easy but there are a few pitfalls, such as:
Base is napthenic and you want to use a paraffinic oil.
    You need 20% Chlorinated Paraffin, your too paraffinic causing an unstable neat product.
    Your biocide package is not compatible.
    You need too much of the base to formulate the material so the product is not cost effective.

I admit my experience with emulsifier bases is limited.  I always made my own, but on very rare occasions I did rely on these materials.  Where you get them is up to you, but there are quite a few suppliers out there who would be more then happy to assist you.  Some of the major players in this market are:
    Mayco (Division of
    Keil (Division of

Is this a complete list, not at all however, it is a list of suppliers that I have had good luck using also in my opinion their technical support is second to none.

Typical Formulation:
Emulsifier Base:          20%
50% Cl Paraffin           10%
Napthenic Oil              QS
Grotan                          3%
Na Omadine               0.3%

Seems like a reasonable formulation that would make a very stable emulsion.  Depending on the emulsifier base you select, that may very well be true, but what if you saw a milky white drop out in the emulsion? That is Cl Paraffin and that is a serious emulsion stability problem.  If you were to rely on the emulsifier base to correct this problem it may not succeed.  You may have to add some fatty acid to hydrotrope the system.  However, if you were to do that, your pour point would rise so as you can see there is a trade off.  These are some of the types of problems you might face.  Recently a reader asked me a product stability question.  They too were using an emulsifier base, and once again the answer was a hydrotrope or a coupler.  As you can see, emulsifier bases can be useful, but care must be taken when formulating with them.

Naturally, with the millions of formulations out there it is impossible to discuss all the possible scenarios but, as always, should you have any questions please feel free to e-mail me in care of the magazine.  Till then,

Good Luck,