Usually, modified rosin is obtained by disproportionation, addition, hydrogenation, and polymerization of the double bond of resin acid molecules and more reactions. And rosin derivatives are obtained by reactions such as esterification, salt formation, and saponification of carboxyl groups. So as to eliminate the disadvantages of rosin such as low softening point, easy oxidation and sometimes large crystallization tendency.
1. Hydrogenated Rosin
Oxidized rosin is formed by partially or completely saturating the conjugated double bonds of abietic acid-type resin acids in rosin under a certain temperature and pressure under the action of a catalyst. Rosin partially saturated with hydrogen is called dihydrorosin, commonly known as hydrogenated rosin. Rosin that is completely saturated with hydrogen is called tetrahydrorosin, also known as fully hydrogenated rosin. Hydrogenated rosin contains 75% dioxyabietic acid, fully hydrogenated rosin contains 1-14% dioxyabietic acid and 66-80% tetrahydroabietic acid. Oxidized rosin has the characteristics of good oxidation resistance, low brittleness, high thermal stability and light color.
2. Disproportionated Rosin
Disproportionated rosin is a irregular transparent solid, getting from gum rosin by chemical treatments to reduce abietic acid content. It is compound of dehydroabie acid and dihydroabtice acid, the DPR is processed through catalytic reaction of gum rosin on proper temperature. The color of disproportionatedrosin is lighter than gum rosin. It also exhibits a good oxidation resistance and heat stability.
In the synthetic rubber industry, disproportionated rosin is used as emulsifier in the producing of various product including styrene-butadiene rubber, chloroprene rubber, acrylonitrile-butadiene rubber and acrylonitrile-butadiene-styrene rubber. Using DPR as an emulsifier, rubber product will improve in cohesion, and the endurance to heat will increase for 25%. The endurance to both abrasion and laceration of this rubber is better than ordinary styrene-butadiene rubber. The cohesion will be greatly enhanced if blending with natural rubber.
Disproportionated rosin can be also used for important component of potassium soaps which serve as emulsifiers to improve and strengthen the quality of synthetic rubbers, a raw material for making adhesives, water-based PSA, pigment, and chewing gum.
3. Polymerized Rosin
Polymerized rosin is one of the important varieties of modified rosin products. It has the characteristics of high softening point, light color, no crystallization, excellent hydrogen resistance, higher viscosity in organic solvents, and low acid value. Rosin polymerization is a dimerization of abietic acid resin, that is, the conjugated double bonds of abietic acid resin are polymerized under an acidic catalyst action into heterogeneous dimer substances. Generally, the softening point of polymerized rosin is below 140℃, and the dimer content is about 35%. If the softening point is above 150℃ and the dimer content reaches 80%, it is called dimerized rosin.
4. Maleic Rosin
Maleic rosin is a high performance modified rosin. It is obtained via a certain chemical reaction between rosin and maleic anhydride. Orignially produced in the 1930s, it was gradually used in industries such as papermaking, paint and ink. It is especially used as a strengthening sizing agent in the papermaking, which not only improves the sizing effect, but also saves the comsumption of rosin. In recent years, the application scope of maleic rosin has been expanded to construction, chemical industry, organic synthesis, etc.
5. Rosin Derivatives
Rosin derivatives are a general term for products obtained by chemical reactions of the carboxyl groups in the resin acid molecules of rosin and modified rosin. Among them, rosin esters and resinates are the most important products, which are widely used in the paint industry. Also there are resinates, rosin amines and others products.