In Your Corner: Dean Thetford Discusses Improving Polymeric Dispersant Technology

Posted by Lubrizol Performance Coatings Team on 06/04/2019

With 30+ years in the coatings industry, Dean Thetford, Senior Technical Fellow at Lubrizol Performance Coatings in the United Kingdom, has seen his share of market trends and predictions about the future of the coatings industry come and go. We spoke to Dean about his background, accomplishments and one topic that he sees as an actual industry game changer—improving polymeric dispersant technology. At Lubrizol, Dean focuses on new market opportunities.

 

“In Your Corner” is a series of interviews with Lubrizol ink and coating experts who share unique insights on key industry challenges and opportunities.
 
What is your background? How did you get to where you are today?
I graduated in chemistry in 1982 with a first-class honors degree and then gained a PhD in organic chemistry in 1985, both at the University of Leeds, UK. The PhD involved developing synthetic methods to anti-cancer drugs. Following a two-year period with Smith Kline & French as a research chemist devising novel synthetic routes to Thyroid inhibitor drugs, I joined ICI Colors and Fine Chemicals (as it was known then, and subsequently as Zeneca and later as Avecia). There, I was a research chemist inventing and developing synthetic routes to novel singlet oxygen generators and colorless infrared absorbers for medical, security, homecare and optical data-storage applications. Since 1990, I have held various technical leader roles guiding a team in the Lubrizol Performance Coatings group to develop novel polymeric dispersants (Solsperse® Hyperdispersants, Solplus™ Hyperdispersants) and thickeners (Solthix™ Rheology Modifiers) for dispersing various pigments and fillers for both aqueous, non-aqueous and 100% systems in coatings, ink and the plastic industries.
 
What is your key area of expertise?
The design of novel polymeric additives, particularly dispersants for use in surface coating and plastic applications. My core skill and background training in organic chemistry provides the ideas to meet targets in new research programs.
 
Looking back over your long career, what would you say is your biggest accomplishment at Lubrizol?
Gosh, that’s difficult to choose one. I am most proud of being able to make innovation contributions and continue to do so in collaboration with other technical colleagues to meet the dynamic needs of the industry and Lubrizol customers.
 
Thinking about what’s important to industry formulators, is there one topic that really stands out?
As the surface coatings industry has faced disruptive changes, I’m excited by our efforts to improve polymeric dispersant technology and what the future looks like.
 
Why do you think the topic of polymeric dispersant technology is so important?
The dispersion and stabilization of pigment or filler particles within a liquid medium is often problematical as the nature of the solid surface can vary widely with their chemical type. Good wetting and stabilization, whether that is electrostatic, steric or electrosteric will only occur when the polymeric dispersant is firmly anchored to a pigment surface and the polymeric tail has good solubility in the solvent medium used and has sufficient chain length (MW) to counteract the attractive forces between solid particles. Typical anchor groups employed in our polymeric dispersants include aromatic centers and various functional groups containing heteroatoms such as amines, carboxylic acids, phosphates and quats, and the polymeric tails can consist of polyethers, polyesters, polyurethanes, polyacrylates and polyalkylenes or combinations of these. The Lubrizol range of polymeric dispersants contain examples and combinations of all these types and we have a continually expanding chemistry toolkit as we employ new raw materials and chemistry to attach the anchors to the polymeric tails.
 
What does it take to create a new polymeric dispersant?
A successful track record of inventing a range of polymeric dispersants hides a more complicated story of research programs and application testing where technical failures are a common occurrence, but are overcome by asking one simple question: Why? If you can answer why a failure has occurred either by factual technical information or possible theories during the research phase of a project, then it is more likely we will generate further ideas to investigate to progress to our final target requirements.
 
In your extensive coatings career, you’ve seen many trends come and go or not play out as expected. Is there one trend that fits that description that comes to mind?
When I began my research journey in 1990 into the technical area of polymeric additives for coatings, one of the first industry trends that was highlighted time and again from customers, conferences and exhibitions was that the coatings industry was beginning to change from solvent to aqueous based systems due to increased pressure on environmental concerns to reduce VOC. Nearly 30 years later, that same prediction is still being made but in those intervening years, we have seen a fragmentation of the types of solvent medium and even elimination of solvent medium used by different coating applications. One lesson I learned is don’t believe all the predictions you hear from the industry. A second lesson is that the fragmentation of this industry with the development of powder, high solids, polar solvent, water-based and 100% radiation cured systems over the last 30 years opened up numerous other opportunities.
 
What factors impact the solubility of polymeric dispersants in the application medium?
There are several factors that impact the solubility of our polymeric dispersants or those of any other additive manufacturer in the application medium. The important ones are the chemistry of the monomers, whether two or more monomer types are used, and the polymer architecture that is employed. So, Lubrizol dispersants can be a single polymer tail with an anchor group at one chain end or random or block copolymers that can have a comb, branched or graft configurations containing a multitude of anchor groups. It should come as no surprise that our best polymeric dispersants are those that contain more than one anchoring group and more than one polymeric chain within the same polymeric structure. These factors also have an impact on the physical form of our dispersants. Over the last 30 years, we have been able to understand the limits and rules of the different factors to innovate excellent polymeric dispersants that are 100% active and are liquid at room temperature. Obviously, there are cost, environmental, product performance and lifetime benefits of doing this, both for Lubrizol and our customers. But, there are also technical formulation benefits for our customers, such as being easier to handle and pourable or pumpable to a customer’s liquid coating (paint or ink) or 100% liquid reactive system while also allowing the customer freedom to develop their formulations to the requirements of best performance whilst minimizing regulatory and labelling constraints, as well as any environmental restrictions.

 

You make chemistry sound like it’s not as complicated as someone might imagine. How is that?

Of course, chemistry and research are never as simple as I have tried to make out and Lubrizol does have several other excellent polymeric dispersants where the polymer chemistry and architecture do not allow the products to be synthesized as 100% active liquids. In these cases, Lubrizol is somewhat constrained in the way they can be made and supplied, usually in the media that they are soluble in. However, more recently, our research group has started to employ alternative monomer technology to facilitate polymer chain disruption in an effort to make 100% active liquid dispersants where it was thought impossible to do.

 

Is this what you mean by “improving polymeric dispersant technology?”

Yes. Early indications are that this is entirely possible where two or more monomers are compatible with one another and our application scientists have seen some synergistic dispersion performance in a limited set of tests. It would be easy to get excited about these early results but there are wider implications and ideas that have been generated from this early work, not least of which is how wide ranging this effect is on our portfolio of products. And, will this type of product have uses in applications other than coatings? Lastly, a particular train of thought that has piqued our curiosity is that if the two or even more monomers are compatible with one another but have distinctly different chemistries, does it impact or enhance the range of solvents that the blend is soluble in? If there are cases where the latter is occurring (enhancement), could the question I have been asked many times, ”Can you make a universal dispersant that is soluble in non-polar and polar solvents?, Oh, and water as well?” be answered with ”maybe, just maybe” instead of my usual thoughtful laugh and a no!

Lubrizol Performance Coatings Team

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