Unknown Resins in Old Paint

Question:

I am an analytical chemist by profession and an industrial consultant. I quite eagerly look forward to your column each month. I often encounter paint problems and your column is a wealth of information.

I have been asked by a local manufacturer (I live in southern Ontario) to prepare an MSDS for an old stock of white primer, which they would like to use. I have data on all the components but two, the alkyd resin and a second component. The company that blended and sold the paint has gone out of business, and we have tried numerous suppliers with no success. If you could point us in any direction it would be greatly appreciated. Thank you for your efforts. R.S.

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Answer:

Thank you R.S. for the vote of confidence. I’m good, but not that good. As a member of the fraternity, you know that consultants wear many hats.
First, I will put on the teacher’s hat. It is almost impossible to know the names of and components in paint suppliers’ formulations. There were roughly 1,000 paint companies in the U.S. Although I am sure that with recent acquisitions there are now fewer. Because of the nature of the business, each paint company could have hundreds of formulations. Do the math. Take oil modified alkyd resin A, grind it into paints with 7 colors (that’s 7 formulations). Take those 7 colors and change the type of drying oil in the alkyd resin (49). Then, do the same thing with 7 different alkyd resins (343). The reasons for these different formulations are different customer requirements. For example, my plant produces green aluminum lawn chairs and my neighbor’s plant produces green wooden lawn chairs. They are both green chairs but require different paints. I could go on, but that may put you to sleep.

Next, I’ll put on my Preacher’s hat. If your client was my client, I would advise him to scrap the old primer. From your description of the paint, it sounds like it is more than a year old. Paints have a finite shelf life. Sometimes the shelf life is only 6 months to 1 year. Most paint suppliers tell their customers not to use paints that have been stored beyond their shelf lives. As you know, alkyd resins “advance” with age. That is, they start to polymerize in the can, increase in viscosity, form skins and gel particles. It may not be too obvious, and a common reaction is to add a little thinner to lower the viscosity.

Now I’ll put on my lawyer’s hat. Old paint can be poor performing paint. It may fall off the product, cause the product to rust in half, cause customer complaints and perhaps product liability claims.

Now I’ll put on my paint consultant’s hat and say it again. Advise your client to scrap the paint. It will be more cost effective to buy new.