Michelin develops high-performance textile-rubber adhesive

Clermont-Ferrand, France — Group Michelin will be leaving a decades-old industry standard behind later this year with the launch of some new lines of tires.

After more than nine years of research and development, the company is ready to start using a high-performance resin adhesive that will replace resorcinol — an isomer of benzenediol that is used in combination with formaldehyde to create an adhesive — as its material of choice for bonding textiles to rubber, according to Olivier Furnon, Michelin's industrial director.

"We have been using in the industry, for textile to rubber, a traditional model that has not been changed for more than 80 years," he said. An adhesive of resorcinol, formaldehyde and latex is usually used to bond textiles to rubber in tire production.

"We will be producing and delivering tires made with this new glue, which is based on a new formula that eliminates completely the resorcinol and formaldehyde," Furnon said.

The new resin, which is currently unnamed, will avoid regulatory constraints in industrial settings where the RFL adhesive would be produced, as resorcinol and formaldehyde are subjected to regulatory limits, Furnon said.

"Eliminating these two products in the raw materials is a smart solution for the safety of the people," he said.

Formaldehyde is a naturally occurring organic compound — CH2O (H-CHO) — that is used widely as a precursor to many other materials and chemical compounds. The U.S. National Toxicology Program described formaldehyde in 2011 as "known to be a human carcinogen."

Replacing the RFL adhesive hasn't been easy for Michelin, he said. The first few years of the R&D process were dedicated to working on new concepts, which seemingly would work as well as an RFL adhesive.

Michelin then tested the adhesive with multiple types of fibres in tire applications, such as polyester, nylon and aramid. The company also tested across various sizes and types of tires, from passenger to agricultural, to find a product that could be used across the board as a replacement for RFL.

"What we are aiming at is that we wanted to find a glue that would be a standard for all applications. And we are quite confident that it will be so," he said. "We are not so far that we can announce today that we will make all kinds of tires with this glue. We will still work on that."

Michelin is moving ahead in mass production of some passenger car and light truck tires, launching the lines with the new glue before year-end 2018, Furnon said. The company is still defining the range of tires and sizes, but will produce at least some sizes of the Michelin Energy Saver and Michelin Alpin tires with the new adhesive before year-end.

Continental A.G. also is working on a replacement for resorcinol. The company disclosed last summer that its tire division is working with Turkish textile reinforcements supplier Kordsa Inc. to develop a sustainable adhesion system standard for bonding textile-reinforcing materials to rubber-based compounds.

Michelin doesn't expect to gain performance with the new adhesive, but it expects the new material to be at least as good as RFL, Furnon said. He hopes the company will make progress with the glue in aviation, agricultural and competition tires over the next five years.