PET specialists spent seven years racing the clock and spending considerable capital in isolating and developing a new molecule to scavenge oxygen.

Matthew Dauzvardis, director, new technologies, Constar International Inc., Alsip, IL

More than 30 years have passed since the 2-liter soft drink bottle made of polyethylene terephthalate (PET) debuted. Since then, the PET container has become ubiquitous, replacing glass in entire categories of food and beverage packaging. US bottled water alone sopped up a fifth of the growing global demand for PET over the last 10 years, researchers at Canadean Ltd. estimate.

The billions of single servings of beer are coveted by PET suppliers, but little progress has been made in wresting market share from glass. Multilayer PET is prone to delamination and is simply too expensive to compete. Monolayer bottles with oxygen scavengers in the plastic matrix have potential, but development work at one firm lay dormant until recent years.

Engineers and chemists at Philadelphia-based Constar International Inc. believe they have solved the oxygen issue with a polymer branded as DiamondClear. Retention of carbon dioxide in bottled beer remains another major hurdle, but in the meantime Constar is enjoying some success with DC-300, a polymer with a new-to-the-world molecule. Hunt’s ketchup launched with an earlier version in 2004. 

The research, development and engineering labs of Constar are housed in the Chicago suburb of Alsip, IL, and the technical staff there spent a significant part of the last seven years on a PET additive that could absorb enough oxygen to deliver two year’s shelf life. The work culminated in July when the Food and Drug Administration gave food-contact approval for m-Xylylenediamine-bis, used in conjunction with cobalt neodecanoate.

Matthew Dauzvardis, director of new technologies, served as project manager in Alsip. A graduate of Northern Illinois University with a bachelor’s degree in biochemistry, he began working in the packaging business as a summer intern with Continental Can. After several years with an instrumentation company, Dauzvardis joined Constar International when Crown Holdings spun off the division in 2002.

Matt Dauzvardis places a PET preform into ILIOP, an instrument that measures oxygen permeation over time. The lab equipment was built in-house by Constar engineers to evaluate oxygen-barrier properties of bottles under development.

FE: When did the scavenger project begin?

Dauzvardis: When Crown spun us off, we inherited the intellectual property of CarnaudMetalbox, which included a nylon monomer with a cobalt salt catalyzer that was very effective at scavenging oxygen molecules. Carnaud really didn’t know how to commercialize the monomer, which they called Oxbar, and ended up licensing it to other firms, including some of our competitors.

A residual of cobalt that Carnaud’s scientists combined with nylon in 1989 was only added as a toner, and there was some level of luck when they discovered that the nylon performed dramatically better than expected. Instead of allowing a steady increase in the transmission of carbon dioxide and oxygen, they found oxygen levels actually declined. But there were clarity issues, and they were pursuing a multilayer structure, which is very capital-intensive to make. When Crown completed our initial public offering in November 2002, we decided to get serious about addressing those issues and started to assemble the scientific team. We knew early on that the solution would involve a monolayer structure, and in 2004 our CEO gave us the challenge to find the molecule that would create that chemistry.

FE: How does the material prevent oxygen from entering the bottle?

Dauzvardis: A polymer is actually moving and changing, with microscopic holes between the different polymeric chains. It’s kind of like spaghetti: when it’s cooked, pasta is amorphous, with lots of places to stick a fork. The barrier molecule is like the meatball in that mass: it grabs the oxygen molecules as they move through and chemically reacts with them but has no affect on other gases.

FE: Did that search involve much trial and error?

Dauzvardis: No. We try to learn from the past and make informed decisions on which molecules to pursue, based on nylon’s performance and what makes it work as well as it does. The process doesn’t permit randomness because it could take a month to get any data back from preliminary tests. We came up with a short list of possible molecules, then retained a molecule company to investigate them.

Unlike university research, which can spend months and months on testing and analyzing and still not come up with a viable product, commercial R&D has to be well thought out and have defined scope because of the money and time involved. In a competitive environment, you have to make a judgment on which molecules you want to run with, then test and validate them. In the end, we came up with a molecule that was new to the planet, which necessitated a food-contact evaluation by FDA. One toxicology test we ran took a year and cost $300,000.

FE: What skill sets are represented on your R&D team?

Dauzvardis: Early on, there were just a few of us, and we worked with outside consultants to help identify molecule developers and chemical producers to outsource different parts of the project. We wanted to accelerate the process, and it took time to develop a team with the right mix. We worked with a number of highly skilled scientists and engineers before we had a group of people who really stood out. There are two PhDs in polymer science and chemical engineering, a biochemist, a chemist, a mechanical engineer and a general laboratory scientist. 

FE: ConAgra debuted a ketchup bottle featuring an oxygen-scavenging polymer in 2004. Why didn’t the project end at that point?

Dauzvardis: We knew there was a little bit of blue sheen in the polymer, but the customer wasn’t complaining. After the initial run of preforms was supplied and filled, it was clear the haze was a problem. When the bottles of Hunt’s ketchup were on the grocery shelves, store lighting made the ketchup appear purple. Fortunately, we had a client who was willing to work with us, and we got serious about finding a solution to both the clarity and oxygen scavenging issues.

FE: What was the next step?

Dauzvardis: There were molecules that we had looked at earlier that we kind of liked. The search involved finding a reasonable compromise between performance, cost and appearance. With DC-200, the color was more like sapphire, and that was abandoned. DC-300 delivered the clarity we wanted, and the oxygen scavenging potential was tremendous. The standard we use is the number of cubic centimeters of oxygen that a gram of material will scavenge. DC-100 scavenged about 125 cubic centimeters, which was less than the 175 cubic centimeters that the previous generation scavenger could remove. DC-300 could remove 250-260 per gram and provided excellent clarity. That extra strength meant we could vary the formulation as desired to deliver longer shelf life where that was critical or deliver a more economical formulation to do the job when shelf life isn’t critical.

FE: Once DC-300’s performance and clarity properties were deter-mined, was your team’s work done?

Dauzvardis: We had the molecular structure, and the chemical houses had put the chemicals together on the bench to get the desired end result, but there still was the issue of scaling it up in big tanks with heat exchangers and pumps to produce thousands of pounds at a cost that wouldn’t be prohibitive. This is where you can have a technical success but a commercial failure. This is a pharmaceutical-purity additive, and it has to both perform at an acceptable level and be made for a package that will be thrown away after a single use for a product that doesn’t cost that much to begin with.