E4S Awards - Asahi Kasei Corp

Asahi Kasei Europe

Project: New selectively hydrogenated SBR for reduced 6PPD usage

Asahi Kasei reported on the enhanced ozone resistance of its selectively hydrogenated styrene-butadiene rubber (HSBR) and its ability to allow reduced usage of 6PPD (N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine) in the rubber compounds.

In its E4S VII update, Asahi explained how further studies have shown that the HSBR makes it possible, to not only reduce usage of the antioxidant/antiozonant, but also to improve mechanical properties, including fatigue resistance.

Moreover, it said, if high-cis butadiene rubber is replaced by the HSBR in a NR/BR blend, then the equivalent NR/HSBR compound showed about twice the fatigue resistance with respect to the NR/BR compound.

Both ozone resistance and fatigue resistance are important properties that governs product-life, noted the company, which is seeking suitable applications for the HSBR other than tire tread, taking advantage of the unique characteristics.

A particular target is the tire sidewall, the part of the tire that is most exposed to UV and ozone, thereby demanding exceptionally high ozone resistance – as well as being constantly subjected to cyclic stress (flexing) during driving.

Usage of the HSBR in the sidewall could eventually reduce the frequency & need of tire replacements due to degradation, said Asahi.

In terms of the commercial status, Asahi said the HSBR is “now being used and tested by many tire manufactures’ worldwide and has received positive feedback.

“Our grades with strategically different functionalisation technologies have developed, catering to tire tread and sidewall applications.”

Asahi’s next goal is to improve the fuel-efficiency of tires incorporating HSBR in treads and sidewalls.

Judging comments

In its entry form, Asahi Kasei has provided solid information about the improvements in tire compound properties achieved including when replacing high-cis butadiene rubber with the new HSBR. Another strong point is that Asahi next aims to optimise the polymer to also deliver improved fuel efficiency, along with the enhance chemical stability and fatigue properties. This, of course, is as well as addressing issues around the potential impact of 6PPD stabilisers on the environment.

Having developed a new catalyst to selectively reduce the double bonds present in SBR – so increasing ozone resistance and allowing reduced usage of 6PPD – Asahi’s focus has shifted to improving the mechanical properties. The chemistry can also double fatigue resistance in tire treads and could improve sidewall performance. But the project entry offers limited technical insights. Supporting data and life cycle analysis would also be helpful to show the environmental benefits during production, use and at end-of-life.