Rosin by itself has low stability due to unsaturation. The utility of rosin resins can be improved via several chemical modifications. These modifications include esterification, hydrogenation, dimerization, functionalization, or any combination of these. Each of these modifications is discussed in the category links below. Since there are so many ways in which to modify rosin; coupled with the fact that there are three distinct sources for the base rosin, make rosin resin product lines difficult to comprehend. Figure 1 is a simplified schematic diagram of the production flow for various rosin resins. Although not shown completely, wood rosin and tall oil rosin can be esterified, hydrogenated, dimerized, or functionalized in the same manner as gum rosin. While not intended as a comprehensive product listing, Figure 1 shows examples of the types of rosin resins currently produced by Eastman Chemical Company. For more information on rosin resins and a listing of products available in North America refer to Eastman publication WA-87, Eastman™ Rosin Products for Adhesives and Sealants. Rosin Acids can be used as tackifiers themselves or as the raw material for specialized derivatives.
- Rosin Esters are produced by the reaction between rosin acids and alcohols. The typical commercial products are methyl, triethylene glycol, glycerol, and pentaerythritol esters.
- Hydrogenated Rosin Resins have improved thermal stability and lighter color due to the hydrogenation of the rosin acid raw material. Once hydrogenated the rosin acid can be used as-is or esterified.
- Dimerized Rosin Resins are produced from dimerized rosin acids, a process which increases the molecular weight, softening point and thermal stability of the rosin acids. Once dimerized the rosin acid can be used as-is or esterified.
- Modified Rosin Resin is a catch-all term for any modification of a rosin resin that is not esterification, hydrogenation, or dimerization. Rosin can be modified by reacting an unsaturated di-acid such as maleic or fumaric acid to the rosin ester molecule. Likewise, it can be modified by reaction with phenol. Another example is the reduction of the carboxylic acid group to a hydroxyl. Modified rosin resins are most commonly used in ink, thermoplastic road marking, and coatings application.
Figure 1: Schematic Diagram of Rosin Resin Production Flow with Product Examples
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.