German speciality chemicals major Evonik has said that it is engaged in research and development work to come up with solutions for recycling rubber and plastics. The company has been making advances, particularly in the mechanical and chemical recycling of plastics and the repurposing of waste rubber, focusing on several products at different stages of the development pipeline.

IN THE MARKETPLACE

Evonik’s portfolio already includes a process additive called Vestenamer, which, it said, is successfully established in the market. The product, which was promoted at last year’s K fair in Düsseldorf, Germany, is a unique process additive that allows waste rubber to be efficiently processed into a tough material, for use in a variety of applications such as road construction, sports or playgrounds.

Originally introduced as a processing aid for virgin tyre production, the additive has also proved to be highly effective in the processing of rubber waste, such as scrap tyres, to generate a rugged work material, the company reported.

Vestenamer, is a polyoctenamer, which improves the flowability of the rubber compound and optimises the crosslink density between the rubber particles, Evonik explained. This makes rubber waste much easier to process and gives the recycled materials several desirable mechanical properties, the company added. Product applications include road construction, but also stable mats for farm animals, it said.

Evonik: recycling scrap tyres

According to the company, every year, a waste volume of some 19.3 million metric tonnes of scrap tyres is generated worldwide – including over 3.6 million metric tonnes in Europe alone. Twenty years ago, over half of all scrap tyres were incinerated to generate energy, while only every tenth scrap tyre was processed into granulate. By now, the volume of the latter has caught up with energy-related processing, it said.

With Vestenamer, Evonik aims to help close the materials cycle for sustainable rubber. In the recycling of scrap tyres and other waste rubber, the addition of Vestenamer is an application that has already proven its worth in production, for rubber products such as floor coverings, mats and stand systems for signposting of road works and barriers.

EFFICIENCY IN RECYCLING

“As a process additive Vestenamer improves the flowability of the rubber compound. As a result of which the material can be processed much more efficiently. The reactivity and polymer structure of Vestenamer are also important here: both lead to a good network density between the rubber particles. This in turn positively impacts the mechanical properties,” said Dr Peter Hannen, market development manager for Vestenamer. “In short, Evonik’s process additive improves both the cost effectiveness of processing and the quality of the rubber parts when rubber is recycled.”

In addition to the economic aspect of providing a cost-efficient raw material, the material recycling of scrap tyres is also becoming more important from the ecological viewpoint. For example, the use of scrap tyre granulate in new products contributes significantly toward reducing carbon footprint by up to one third, compared with products that do not use a recycled material. A closed circular economy of rubber also alleviates the global scrap-tire problem.

Vestenamer from Evonik has been used as a process additive in the rubber industry for many years, and is manufactured in the Marl Chemical Park (Germany).

IN TESTING

Evonik revealed that it is currently working with a large waste disposal company to optimise the mechanical recycling of polyethylene, which is processed in large quantities, especially in packaging films.

Mechanical recycling involves separating and cleaning synthetic materials in order to directly reuse them as polymers. The challenge is, however, that this recovery process affects the quality of the recycled material. Evonik is currently testing an amorphous polyolefin-based additive as a potential solution to the quality challenge.

The Evonik additive Vestoplast that is primarily used in hot-melt adhesives may be the key to making that possible, the company said. It can specifically improve the impact strength or flow properties of polyethylene, which may be helpful for reusing recycled plastic, for example in injection moulding, it reported.

IN DEVELOPMENT

Another problem with the mechanical recycling of polymers involves unpleasant odours, both in the recycling process and in products made from recycled substances. Evonik is testing existing odour-absorbing products from its Tego Sorb brand to see if they can provide a solution. “The odour-absorbing products of the Tego Sorb brand may offer a solution for neutralizing such smells,” the company said.

In contrast to mechanical approaches, chemical recycling involves breaking plastics down into their individual components, meaning that polymers are turned back into monomers. These monomers can then be converted to polymers of the desired quality to close the materials cycle.

Evonik is currently examining the feasibility of solvolysis based on alkoxides for polyethylene terephthalate (PET) plastics. The process breaks these materials down into the two monomers ethylene glycol and dimethyl terephthalate. PET plastics are used, for example, in beverage bottles. Evonik is already offering the alkoxides that would enable this chemical recycling as part of its product range for manufacturing biodiesel.