A common method to improve stability is to hydrogenate the rosin molecules as shown in Figure 1. Hydrogen molecules add to the double bonds of the rosin acid which greatly increases the molecule’s resistance to oxidation and improves its color. The hydrogenation process can be controlled so that the rosin is either partially or fully hydrogenated. Partially hydrogenated rosin is produced by Eastman Chemical Company as
Staybelite-E™ and completely hydrogenated rosin is branded as
Figure 1: Stabilization by Hydrogenation of Rosin Molecules
Like rosin resins, hydrogenated rosin resins have a wide span of compatibility with almost all polymers. They are well known for their peel and tack contribution to the adhesive. They have specific advantages over non-hydrogenated rosin resins:
- Lighter color.
- Significantly improved stability.
- Less to no skin sensitization (depends on the degree of hydrogenation).
- Less UV absorption, thus making them suitable for UV curable polymer based adhesives.
- Imparts only a slight decrease of cohesive strength, especially in block co-polymer systems.
- Can be used in amorphous polyolefin based adhesives.
For more information on rosin resins and a listing of products available in North America refer to Eastman publication
Eastman Rosin Products for Adhesives and Sealants.
Since transportation of some types of rosin resins is not feasible and all products are not produced at each manufacturing site, the availability of rosin resins varies regionally.