Modified rosin is a very generic term for any rosin resin that is changed in some way other than esterification, hydrogenation, or dimerization. Generally these products are made for specialized purposes or markets other than adhesives. The most common modification of rosin is what is knows as a Diels-Adler reaction as shown in Figure 1. In this case, the reactants are specifically pimaric acid and maleic anhydride, although fumaric acid can also be used.
Figure 1: Maleic Modification of Rosin
The maleic or fumaric anhydride molecules can then hydrate in the presence of water to form a di-carboxylic acid functional group. This produces a rosin derivative with three carboxylic acid groups. The increased acidity makes the modified rosin especially useful in ink, varnish, and coatings applications. Acid modified rosins can also be esterified to form acid modified rosin esters. Maleic modified glycerol rosin esters such as
Lewisol™ 29-M are also used as binder resins for thermoplastic road marking compounds.
Another common modification of rosin is the reaction with phenol to make phenolic modified rosins and rosin esters. These products have a combination of acidic, ester, and hydroxyl functionality that make them useful in inks, varnishes, heat set inks, and coatings. It is also possible to reduce the carboxylic acid group of the rosin acid to a hydroxyl group thereby forming rosin alcohol. While this product cannot react with alcohols to form esters, it does have unique properties as a primary alcohol attached to a very large alkyl group. This makes rosin alcohol useful in coating and surfactant applications where the hydroxyl group provides desired functionality. Some of the modified rosin products produced by Eastman Chemical company are:
Maleic Modified Rosin Resins:
Fumaric Modified Rosin Resins:
Phenolic Modified Rosin Resins:
These products are manufactured in the Eastman Chemical Company plant in Urupan, Mexico. They are distributed throughout Latin America, but availability may be limited in other regions.