At Arburg Technology Days, people were talking about - and sniffing - a leather dice cup made on an injection molding machine.
Alexander Stoll handed out hundreds of the brown cups during the event, held March 22-24 at Arburg GmbH + Co. KG's machinery factory in Lossburg. Stoll heads the Kollamat molded leather business for Bader GmbH & Co., a major German supplier of leather interiors for high-end cars.
The cup is made of 60 percent leather fibers and 40 percent low density polyethylene. But Bader, which compounds the leather/plastic materials, can customize the ratio, and use different resins, to meet desired properties.
``Sometimes we need two or three plastic [resins] in one compound to make it special, the characteristics of this new material,'' said Stoll, who has a plastics engineering background.
Stoll said products can be molded with as much as 80 percent leather content.
The company also blends in biopolymers extracted from the leather production process.
About five years ago, Bader management decided to explore alternatives for its scrap leather. The company in Göppingen, Germany, was selling the waste pieces to Pakistan and other Asian countries, where they became handbags and other goods.
``But the market, it's not very stable,'' Stoll said. ``Sometimes we sell the raw material for a good price. But sometimes they pay less, or even next to nothing. It's very up and down. So this was the reason to say, can we do nothing more with the leather?''
Bader technicians talked to about five injection press makers about its idea to mix plastic and leather, but got no takers until they approached Arburg, according to Stoll. Right away, Arburg - which has a reputation for trying unusual things, like injection molding ceramic items - agreed to test the idea.
The first product was a brown leather coffee cup, complete with a graceful, molded-in handle.
Executives of the leather company directed Stoll to buy a 100-ton Arburg for use in Bader's lab.
First, the leather is cleaned and finely shredded in a mill, to get a fluffy fiber. Then Bader uses a small extrusion line to compound the material into pellets - mainly in black, brown and gray, but color can be added.
Textured and natural, the Kollamat molded leather gives parts a warmer feeling than hard plastic, Stoll said. On some parts - tool handles, knobs for a car's stick shift, a grip for a hiking stick - a big selling point is leather's ability to absorb sweat and give a good, comfortable grip.
Bader also is promoting Kollamat for automotive door panels and seating, as a replacement for vinyl. By adding glass-fiber reinforcements, Bader can improve the physical properties of the material. Kollamat also can be foamed. Stoll said Bader is working on some automotive projects, but he declined to give details.
Bader is willing to mold the final product, provide the pellets or sell the leather fibers to customers.
Stoll said it's so new that Bader hears a lot of suggestions for applications, even toys. He pulled out a little toy horse with a saddle - a real leather saddle that could be mass-produced on an injection press.
