Renewable technology leads to developments for Kuraray

TOKYO—Two of Kuraray Co. Ltd.'s newest polymers bring new approaches for applications, one through a new monomer and the other through a balance of different polymers.

Using a new renewable monomer called B-farnesene, Kuraray has developed a new hydrogenated styrene farnesene copolymer that has sound damping properties and high flowability. It can be used in many applications where traditional hydrogenated styrenic block copolymers are used, said Erich Klein, elastomers business unit marketing manager for Kuraray America.

Kuraray worked with Amyris Inc., an industrial bioscience company located in Emeryville, Calif., to create HSFC. Amyris uses genetically engineered yeast cells to convert plant-sourced sugars such as sugarcane into target molecules through a fermentation process. Among other molecules, Amyris developed farnesene, which Kuraray uses in place of or in combination with butadiene, styrene and isoprene to make HSFC, Klein said.

"There's an appetite in the world for more bio-based polymers, so we began researching multiple options including farnesene," Klein said. "In our R&D group, as they began evaluating farnesene, they found that in addition to being bio-based, it also provided some other properties that were really intriguing. If you look at the polymer structure itself, HSFC has more branching while traditional HSBC's have a more linear structure."

The modified structure gives formulators different properties to work with, including a few key differentiators that separated it from Septon. HSFC has a high tan delta over a wide temperature range, which correlates to improved sound and vibration dampening properties beyond what traditional styrenic block copolymers can provide, Klein said.

This could be especially helpful in applications such as sound deadening or attenuation in the automotive industry. Following trends of electric cars and light-weighting vehicles for better fuel efficiency, controlling sound becomes more important because the vehicle acts more like a hollow box.

"It's a problem with managing rattles and general low frequency sounds within the range that we hear that are becoming more of an issue for automotive companies," Klein said. "Customers can potentially use this to have better sound-dampening qualities. The high tan delta at a wide temperature range is very differentiating."

HSFC is very soft and has a high melt flow rate, reducing the need for plasticizer in many cases," Klein said, which eliminates the issue with plasticizer blooming to the surface. In markets where styrenic block copolymers are used, such as compounders and adhesive manufacturers, thinner films are more useful.

"We're talking microns, with very, very thin films," Klein said. "In general, the better the polymer flows, the more apt you are to make a quality film."

HSFC is also inherently tacky, which can be a useful quality in the adhesive, sealant and coating markets, Klein said. But it also could assist with rubber grip, such as with athletic gloves.

The farnesene monomer is manufactured in Brazil, and polymerized and hydrogenated at Kuraray's Kashima, Japan, facility, which produces several other polymers as well. There was some capital investment involved, but it wasn't a major investment, Klein said.

HSFC is being evaluated globally by a number of companies, from rubber compounders to adhesive companies, to film manufacturers. It is currently available to the market with an non-disclosure agreement, Klein said.

In February, Sumitomo Rubber Industries developed a winter tire using liquid farnesene rubber from Kuraray as a performance-enhancing additive. The process utilizes the same farnesene monomer used to develop HSFC.

Finding a balance

In addition to HSFC, Kuraray introduced another polymer with multiple applications, Kurarity.

"There are a couple of different polymers that are used currently that have really good properties, but everybody was wanting something a little bit different," Klein said.

One, polymethyl methacrylate (PMMA), is a polymer that produces a clear, plastic-like sheet that has very good weatherability that can be used for products like aquariums. However, it isn't very soft or moldable. The other, hydrogenated rubber, allows for many moldable shapes, but can't be made clear.

Kuraray's R&D group developed Kurarity using a living anionic polymerization process and a unique catalyst. Kurarity has properties of both an elastomer and PMMA.

"It has the clarity of a PMMA, the weatherability and the properties of a PMMA but you have other properties similar to elastomers," Klein said.

Kurarity comes in various grades, blending different levels of PMMA content and molecular weight. Grades with higher PMMA tend to be used in molding applications like soft clear cell phone cases, to interior light guides in automobiles, Klein said. Lower PMMA content grades work for various types of adhesives.

"We do different combinations, and you get different properties. That's where the art comes in, and that's where our customers trial different grades to produce different compounds or different end parts that have the properties they want," Klein said.

Another differentiator for Kurarity is a narrow molecular weight distribution, due to the polymerization technique. Used in an adhesive, Kurarity enables clean removability, without residual monomers or oligomers. That allows it to be used for applications like painter's tape or removable labels, even over a long period of time, Klein said.

Whether in a more solid form or used as an adhesive, it maintains its clarity, which allows for different types of clear compounds. It also can be produced with different colors, and has good paintability.

Kurarity is produced in Niigata, Japan, where Kuraray substantially invested to build a plant, which employs about 20, for the product.