## Coating Matters | The 3 Stages of Product Development

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Process development is taking a product concept through three stages of development:

• lab scale
• pilot scale
• production scale

In the world of fluid coating, the question is not whether you can move between these layers of process development for a given product, but how accurate will this transition be? Product development efforts can become more accurate and predictable if the efforts concentrate on one process system. Having a process engineer who is an expert in a specific coating line will help determine the variables that scale and the variables that need to be monitored through the scale-up process.

Assumptions

Engineers are notorious for making mathematical assumptions to simplify and complete a project. The key is to make assumptions with equipment only after you have an understanding of how the equipment interacts with the fluid. A good starting point is to run a series of fluid “families” through the scale-up to understand what the effect of process and product variables are to the final product outcome.

As an example, take a Newtonian fluid, a polymeric shear thinning fluid, and a shear thickening fluid and run coating trials on the lab, pilot, and production scale with process variables fixed. Then utilize one fluid and repeat the procedure for the process variables through the various scales of production efforts.

This process should take advantage of the principles of Design of Experiment (DOE) statistical analysis. Taking a statistical approach to studying product and process variables can produce mathematical functions and find factors that can reduce development time. This roadmap will allow the process engineer to make some significant reductions in time to develop a variety of products for a given process line.

Simulations

To get started and move between existing lines of different scale, it’s is a good idea to build models. These models should work from a finished product and work backwards. What I mean is that once the coated product is in the final sale-able form, the process engineer should work through the steps that were required to arrive at the production scale. What was a linear function? What mathematical factors could carry products from one level to the next? What difference was recognizable from one lot of fluid to another?

There are some governing equations for coating and curing a product, the key is to account for the equipment process and fluid/substrate product differences for your industry. In all cases the best place to start is with a rheological map of the fluids of interest and an understanding of the surface energy and surface tension associated with the fluids and substrates.

This system of product first on an existing and stable process coating system provides advantages of building empirical process models that can provide theoretical analysis on future product development efforts. Incorporating lot-to-lot variability information will also provide valuable input into the process response map developed by the engineer over time.

Let’s take an example. If you were designing a product for the pressure-sensitive adhesive industry, you have set criteria that you are looking to maximize—the adhesive peel force, the shear force, and the thumb appeal. Peel and shear work adversely with the level of tackifier added to the rubber component in a given adhesive. Variations of this adhesive chemistry can be limited to one that develops high shear at the expense of peel, one that develops high peel at the expense of shear, and one that tries to balance the two characteristics.

These three chemistries would be run through the lab, pilot, and production scales of equipment, noting the equipment differences (as detailed as possible). Then, after the product result testing is complete, one of these chemistries would be run through the gamut of equipment, varying the process variables to understand the effect of line speed, flow rate, coating applicator mechanics, and curing effects. Comparison between control settings, process effects, coating window, and quality measures would provide insight into future development efforts.

Conclusions

So in the end, what can we say about process development from lab to production scale? While understanding the scale of a product on one lab coating line and transferring to any other pilot or production line may be a daunting task, over time, a process engineer can develop scaling factors to make the transition from one scale to the next easier and more predictable. This long range approach of repeatability requires supportive management that understands the value of turning the art of process development into a science with attention to detail, building mathematical models, and providing consistency for a product development chemist.

If you are interested in discussing this concept further, contact me at This email address is being protected from spambots. You need JavaScript enabled to view it. or (612) 605-6019.

Mark D. Miller, author of PFFC's Coating Matters column, is a fluid coating expert with experience and knowledge in the converting industry accumulated since 1996. Mark holds a Bachelor's degree in Chemical Engineering from the Univ. of Wisconsin-Madison and a Master's degree in Polymer Science & Engineering from Lehigh Univ. and a Juris Doctor from Hamline Univ. Mark is a technical consultant and CEO of Coating Tech Service LLC. He has worked in web coating technologies and chemical manufacturing operations and is a certified Six Sigma Black Belt trained in both DMAIC and DFSS disciplines. Coating Tech Service provides process troubleshooting and project management for precision coated products. Mark has extensive process knowledge in high precision coating applications including thin film photo voltaic, Li-Ion battery, and optical systems technology. Mark has been integral to new developments and technology that minimize product waste and improve process scalability.