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High shear mixer
I know there have been discussions about high shear mixers before, but I couldn’t figure out what kind of head they were using. I’m looking for a good mixer for small scale (<10 lt) emulsions. Any experience with these instruments?
https://www.amazon.com/Gowe-Stainless-Laboratory-Approved-Handling/dp/B00G1GJGRK
https://www.amazon.com/Digital-Emulsification-JRJ300-S-Emulsifier-Emulsifying/dp/B01IK3PQ3O
Thank you
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7 Replies
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Go for local supplier, tell them your requirement, they will guide you.
Silverson is the best company for the small mixer
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Do you actually need a high shear mixer?
When I was involved in formulating emulsion products, the occasions I required a high shear mixer were few and most often if a high shear mixer was necessary I would reformulate to be able to avoid high shear.
All of this was to offer the larger scale manufacturing a more reliable procedure and avoid remixes or dumping of failed batches.
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Johnb, I’m curious why you avoid high shear? What are the disadvantages?
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I am a big believer in the idea of KIS - Keep It Simple.
There are several reasons why I avoid high shear mixing:
1. High shear necessitates a high energy input. This energy has to be dissipated somehow and this is usually in the form of heat. The head of a high shear mixer is invariably hot (or at least warm) after use. The temperature reached at the interface of the shearing surfaces can be very high. This temperature effect can have numerous adverse effects on the product being emulsified, not only in delaying cooling but there is a danger of denaturing heat sensitive components.
2. Polymeric materials can easily be destroyed or at least partially depolymerised by the physical shearing action (and high local temperature at the shearing interface). Carbomers are particularly susceptible to this and it is easy for a carbomer dispersion to lose almost all of its desirable properties after just a short time in an Ultra Turrax. Cellulose ethers and similar behave in a similar way but they do tend to be somewhat more resistant.
3. High shear mixers are (compared with a paddle stirrer) very expensive both in initial cost and in maintenance - it is much more difficult and time consuming to clean a high shear mixer head than a simple paddle (this may not count for much on a laboratory scale but can be significant in tonnage quantities).
There are other reasons which I cannot bring to mind at the moment but the above should be enough for starters and remember Keep It Simple.
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As an additional point, there’s a non-formulation reason that a great many professional-level formula’s have started to use high-shear mixing, even when it’s not needed - the increasing rise of dual- and triple-function mixing vessels in production facilities.
One of the formulating guidelines I was first taught when I started as a cosmetic chemist was “Just make it successfully/stably in the lab, and your job is done. It’s the production department’s job to figure out how to make it on a larger-scale.” Well, several spectacular failures later (both my own and those of co-workers), and I learned differently. As a professional cosmetic chemist, you MUST formulate/process with an eye towards scale-up and scale-down issues, or you run the risk of making a great product in the lab that cannot possibly be made on larger scale.
So, as a professional cosmetic chemist, you will be aware of the equipment that will be used to make your formulas in a pilot plant and in production, and the limitations/parameters of that equipment. You will be careful to restrict your procedures in the lab to parameters that scale up to your production facility. (Cooling small batches of an emulsion in an ice bath is the classic example of violating this guideline).
But now, if you already know that your formula will be made in (for example) a Lee Tri-Mix Turbo-Shear mixer, you will also know that that at least one or two of the reasons that Johnb cited for not using a high-shear mixer won’t apply. And there may be additional issues balancing the extra costs involved in running and cleaning the mixer, as well. Having spent quite a large chunk of capital equipment money on purchasing one of these mixers, your production department will be under a lot of pressure to justify the purchase - and they will likely put pressure on R&D to use the mixer whenever possible, even if the formulation doesn’t really need high shear.
So that’s some of the history behind this. But if you are formulating on a small-scale, or for a supplier making reference formulas, all you may hear is the “it’s really important to use a high-shear mixer” part, and not the “so Oscar the Production Manager doesn’t get in trouble for spending more money than a Tesla costs on new mixing equipment” part.
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Beautifully summed up by Perry: “A homogenizer is more appropriate for making fine particle emulsions (creams). A high shear mixer is more appropriate for making most other cosmetic products like shampoos, body wash, conditioners, gels, etc. Ideally, you would get both but if you could only get one, I’d got with the high shear mixer. Most people in the cosmetic industry use Silverson mixers.” -
Thanks for the enlightenment about high shear mixers. I always thought that was what you were supposed to use. I have a Silverson and love it but am considering an overhead mixer for the very reason johnb mentioned - it’s a “PITA” to clean the mixing heads and attachments.
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