Catalyst helps PU firms move to new blowing agent

Clarification: Reworks the fourth paragraph to better explain Shepherd Chemical’s catalyst research.

Interview article by Al Greenwood

BALTIMORE (ICIS)–Bismuth-based catalysts used to speed up the reaction that creates polyurethanes are helping companies adapt their formulas to a new generation of blowing agents, a component critical to making foams, the head of research of US-based Shepherd Chemical said on Tuesday.

The product is the company’s BiCATs 8840 and 8842 water-stable bismuth catalysts. It is one of three finalists for the Polyurethane Innovation Award, given by the Center for the Polyurethanes Industry during the Polyurethanes Technical Conference.

Shepherd’s catalysts are used to speed up the reaction between the two main constituents of polyurethanes, isocyanates and polyols, said Rob Hart, head of research for Shepherd Chemical. He made his comments on the sidelines of the conference during an interview with ICIS.

Shepherd started researching bismuth-based catalysts back in the 1960s, the company said. In the mid-1990s, the company started working more directly in the polyurethanes market.

Back then, polyurethane formulators were not eager to find catalysts that were compatible with what now make up the fourth generation of blowing agents.

Instead, they wanted a catalyst that was less toxic, Hart said. “It was appreciated that some catalysts for polyurethanes were really toxic and causing some issues for consumers, particularly mercury.”

Bismuth addressed the toxicity issue, but it reacted to the water in a polyurethane system, he said. The result was an inactive form of bismuth.

Shepherd spent more than a decade trying to find a solution, Hart said. “We finally had a hit a few years ago.”

It found a ligand system that can wrap around the bismuth and protect it from water, while still allowing it to create the polyurethane, Hart said.

Meanwhile, the need to find a replacement catalyst for polyurethanes had become much more urgent because regulators are in the process of phasing out one of the main classes of blowing agents.

Blowing agents are a key component for foam polyurethane systems. They create the cells that are responsible for the impressive insulating properties of the material.

However, blowing agents are not problem free. The latest generation, which include hydrofluorocarbons (HFC), are ozone friendly, but they are also powerful greenhouse gases.

Regulators are in the process of phasing out these blowing agents. In the US, the Environmental Protection Agency (EPA) is developing a list of alternatives to HFCs under its SNAP programme, short for significant new alternatives policy.

Hydrofluoroolefins (HFOs) are among these alternatives, and they make up the fourth generation of blowing agents.

Replacing blowing agents is not easy because new materials can alter the performance of the other components of the polyurethane system.

In the case of HFOs, they can be incompatible with traditional catalysts, Hart said.

“It causes poor shelf life of the resin, it causes foam collapse. It just has a number of challenges that has to be worked through,” he said.

While Shepherd initially developed its bismuth catalysts to address toxicity concerns, it turns out that the material is also compatible with HFOs.

“The convergence of our innovation with the hydrofluoroolefins has really been fortuitous and it will allow formulators to make the greenest resins yet,” Hart said.

Currently, Shepherd is looking at what qualities might change with the use of BiCATs 8840 and 8842, he said.

“Right now, we’re just at the beginning of this. Our patent application was just published in July,” he said. “What we’re seeing right now in most formulations, it’s literally a drop-in for the existing metal catalyst.”

The other finalists for the Polyurethane Innovation Award are Huntsman’s VITROX HC 98010 Polyol with SUPRASEC 9801 Isocyanate and Dow Chemical’s VORA Zzz foam technology.

The Polyurethanes Technical Conference is hosted by the Center for the Polyurethanes Industry of the American Chemistry Council (ACC). It runs through Wednesday.