Henkel and LIKAT are working on new bio-based "detachable" adhesives

In the BIOVIN project, the Leibniz Institute for Catalysis Research (LIKAT) and Henkel have produced new building blocks for innovative bio-based adhesives that can be deglued on the basis of carbohydrates and vegetable oils. For example, this reversible combination will greatly improve the ease of repair and recyclability of electronic products or household appliances.

The researchers also obtained interesting secondary results, in particular the development of a new, highly selective catalytic process for the production of divinyl ether. The project is funded by the German Federal Ministry of Food and Agriculture (BMEL) through the project management organization Fachagentur Nachwachsende Rohstoffe e.V. (FNR).

In the Biovin project, new polyols were successfully produced at high yields and low cost from commercially available bio-based platform chemicals. The researchers took two approaches to these intermediate products: First, they tested polyols as reactive components in polyurethane adhesives. The properties and key data of the obtained polyester polyols are similar to those of similar petrochemical based polyols.

Polyols, on the other hand, are processed into new bio-based multifunctional divinyl ethers (DVE). To this end, LIKAT has developed a catalytic synthesis method that can convert almost any bio-based polyol or phenol into vinyl ethers. Compared with the most mainstream commercial processes to date, the yield of the process is as high as 98%, the formation of unwanted by-products is significantly reduced, and it has higher selectivity, efficiency and environmental protection. Research is still needed to find efficient and cost-effective catalysts.

Targeted "debonding"

Researchers have prepared new adhesive formulations using vinyl ethers, which could be an alternative to the commercially successful acrylic ester system. The study found that they have similar curing behavior, but have poor adhesion to metals and better adhesion to plastics. Other advantages include that they are less toxic, have a lower odor, and that they are derived from renewable raw materials.

In addition, divinyl ether (DVE) provides the basis for adhesives that can be specially "degumming" by heat, light or acid. This enables the recycling of electronics and household appliances and supports the circular economy. In the Biovin project, a total of 14 different prepolymers were produced from divinyl ether (DVE) and commercially available bio-based dicarboxylic acids. No additives or catalysts are required, and in most cases no solvents are required. It was confirmed by spectroscopic studies that the debonding was achieved by thermal cracking and chemical cracking under mild experimental conditions. Although further optimization is still needed, the developed prepolymers have shown great potential for use in new, recyclable adhesive systems.