Sunday, March 10, 2013

Hydro-Alcoholic Gel With No Air

English: A industrial static mixer Italiano: M...
English: A industrial static mixer Italiano: Miscelatore statico industriale in acciaio inox (Photo credit: Wikipedia)
When I first started working on formulation preps for the pharmaceutical industry I worked with a very intelligent but quite quirky senior scientist.  By quirky I mean that he would occasionally dress in a bunny suit and order carrots at a local diner only to be subsequently tossed out. That is another story for another time.
He was  tasked with making a hydro-alcoholic gel that was clear with no air bubbles. The formulation was rather straightforward but scale-up and manufacture was quite difficult. There were a number of problems. First we were supposed to work with existing equipment. This meant that using dish bottomed tanks and poorly positioned high shear mixers. Further, since this was a potential explosion risk we had to use explosion rated mixers.
Our budget was small but there was no way that we could use existing equipment. We had to think of ways to invest in equipment to perform this task that did not require significant capital. Here is what we did.
We fabricated a tall, thin flat bottomed mixer out of rolled steel. It helped that we had a shop that our mechanics and machinists that was so well equipped that they could probably build a spaceship if  needed. Second, we ordered a mixing blade that was low shear with high pumping action. The blade was roughly the same diameter as the tank (although slightly smaller). For the mixer we had to purchase an air mixer to meet the explosion proof needs. The results were fantastic. We created an airless gel that looked and performed great. Too bad the project was cancelled before were able to get it launched.
I would love to try to replicate this process with a static mixer someday. I have attached a picture above a static mixer for those of you who are not familiar with these mixers. These mixers were not widely used in pharma the early 1990's when I was involved developing this gel.
Here is a link to Ross who makes a variety of static mixers to meet all needs.
Ross Company Website

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