AKRON—For several years Eastman Chemical Co. has been working on the latest addition to its Crystex-brand family of insoluble sulfur additives, and now the new product is up for an award at an industry event.
The firm's Crystex Cure Pro is a nominee for the 2019 Tire Technology International Awards for Innovation and Excellence, with the winners being announced at the Tire Technology Expo March 5-7 in Hanover, Germany.
Eastman's Cure Pro product builds on prior Crystex products, including Crystex HS and Crystex HD, yielding an even more dispersible, thermally stable product than has been offered in the past, Fred Ignatz-Hoover, an Eastman technology fellow, said during a recent interview.
"For this customer, this means improved handling, ease of material transfer, ease of weighing and less headaches in manufacturing products," he said.
Decades of history
This year marks the 75th anniversary of the Crystex line of insoluble sulfur. The importance of insoluble sulfur in the rubber industry was first recognized in 1932 by a Goodyear chemist named Herbert Endres, according to Ignatz-Hoover.
Endres patented a blend of soluble sulfur with insoluble sulfur to prevent bloom during mixing. In that time period Stauffer Chemical Co. bought National Sulfur, he said, and the use of insoluble sulfur started to take off because of its beneficial features.
"The insoluble sulfur allows tire companies and rubber manufacturers to compound materials to higher loadings of sulfur and have an opportunity to manufacture without the interference of bloom," Ignatz-Hoover said. "The goals of the product for 80-plus years now have been to improve the thermal stability and the dispersibility of insoluble sulfur."
The Crystex brand itself has been through a number of ownership changes over the years. Ignatz-Hoover—who has been with Eastman and predecessor companies Monsanto, Flexsys and Solutia since 1986—said he believes it was Stauffer Chemical that first trademarked the brand.
And as tire manufacturing has evolved over the years, so have the Crystex offerings. In 1975, the high stability Crystex HS was introduced, followed by Crystex HD, a high dispersion version, in 1998.
Next step forward
Crystex Cure Pro is the next evolution of a brand that has endured over the years, Ignatz-Hoover said. Its dispersion characteristics are significantly faster than Crystex HD, allowing manufacturers to optimize cycle times.
"We've also engineered into the product improved thermal stability characteristics," he said. "We estimate that customers can expect to see improvements in processing temperatures on the order of 4°C to 6°C. In some cases we've seen customers able to improve their processing by as much as 10°C."
Combining the thermal stability with the improved dispersion, he added customers can mix at higher RPM, which can cause higher heating in the mixing process but results in shorter mixing times and increased throughput. In addition, customers can run downstream processes such as calendering faster, with some reporting improvements of 10-15 percent in actual line speed rates—all without issues related to sulfur bloom.
"This allows for higher productivity and significant cost savings, while still producing very high quality products that are associated with the Crystex name," Ignatz-Hoover said.
Another Cure Pro feature that benefits customers, he said, is that the additive is roughly 10 percent oil products, compared to other grades that can be 20 or 33 percent oil. That means the customer sees more sulfur in the compound, saving floor space and storage areas and resulting in operational savings.
The first public presentation on Crystex Cure Pro was in October 2017 at the ACS Rubber Division International Elastomer Conference in Cleveland. Ignatz-Hoover said Eastman has been working with its alpha partners in developing the new line for about the past four years, work he said was invaluable to the product's development.
"In the tire industry, mixing and calender operations at production scale are extraordinarily difficult to simulate in the laboratory," he said. "So we designed and worked on engineering the product in the laboratory, and then we took those features which we felt were important, trialed them in the factory and learned what works and what doesn't work."
That was helpful in streamlining the development process, having access to production-scale equipment and operations so that Eastman and its partners could run tests in real time and perform long-term trials as well.
The company first began commercial production of Cure Pro at its factory in Nienburg, Germany, in 2017, and then began making the additive at a facility in Malaysia last year. Investment and development costs weren't disclosed.
"We strongly believe in the technology and it's already seen a lot of commercial use by customers," said Ajit Joshi, an Eastman Chemical segment market manager.
Ignatz-Hoover said Eastman has commercialized the product with customers beyond its alpha partners, and feedback has been extremely positive.
"It's not just for tires," he said. "It can be used anywhere insoluble sulfur could be used, such as hoses and belts. ... We feel this is going to be a very important product in our portfolio and we think customers are going to be very excited at the benefits they will see using the product."
When asked about the price point for Cure Pro, Joshi said it is a premium product that will help customers gain more value from their end goods, and both parties can then gain a fair share of this value. "That makes investment in new innovations possible," he said.