Wednesday, July 23, 2008

The Disposable "Motionless Mixer"

Contributed by Irving J. Arons, Product Technology 1969-1994.

In the early 1970's, MPB Corporation asked Arthur D. Little's Product Development Section to develop a "package" for two-part reactive adhesives that would not require mixing by the end user. I was the case leader for this effort.

After considering several different packaging techniques, including a two-part aerosol delivery system, the development team decided to use a disposable version of the Kenics Motionless Mixer, developed and patented earlier by an ADL team and licensed to the Kenics Corporation. The Kenics Motionless Mixer was composed of a series of eight bow-tie like stainless steel elements, bonded end to end and at angles to each other, within a stainless steel tube. The idea was to break up and disperse materials that flowed through the tube. It was used in the food and civil engineering industries for mixing air into water in ponds and lakes and for blending disparate food materials. The only problem was that the smallest of the Kenics mixers cost $100 each, well beyond what a throw-away product for mixing adhesives could bear.

The Stainless Steel Kenics Mixers

Arthur Drennan, one of the team members, was able to find a plastics molder capable of injection molding a unit of 8 bow-tie elements in the correct configuration, that could then be placed inside a hollow plastic tube which, when connected to a dual-chamber syringe, would perform the required mixing for two-part adhesives. The resultant mixing element was produced for pennies each and successfully fulfilled the requirements of the client.

Injection molded plastic bow-tie elements

Today, versions of this disposable mixer can be found in many hardware stores, packaged with two-part epoxy and acrylic adhesives, and is also found in virtually every dentist's office, used to mix the reactive components placed into the mouth to produce molds for dental bridges and caps and for cements to hold braces in place. Unfortunately, we were unable to patent this development.

Prototype assembled dispensers

The picture below shows how the Kenics mixer works, showing the mixing of a red and blue colored viscous material to create a "mixed" green composition:







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