Disproportionated rosin (DPR) is a compound consisting of dehydrogenated resin acids (dehydro-abietic acid) and hydrogenated resin acids (dihydro-abietic acid). It is produced from gum rosin by heating or acid treatment. DPR is commonly used in the form of a soap as an emulsifier in various products such as styrene-butadiene rubber, chloroprene rubber or acrylonitrile-butadiene-styrene rubber.
Disproportionated rosin is obtained by heating rosin mixtures at temperatures of 180-350 C for a sufficient time to reduce the abietic acid content to below 15%. The disproportionation process displaces the hydrogen in the abietic acid of the rosin to convert them into isomeric acids, particularly dehydroabietic acid, which lack nonbenzenoid double bond conjugation and are therefore more stable to oxidation than abietic acid.
Used as an emulsifier, rubber products have greater cohesion and heat endurance. Compared to ordinary styrene-butadiene rubber, the rubber with DPR content has greater abrasion and laceration endurance.
DPR has other functions, such as being an important component of potassium soaps which serve as emulsifiers to enhance the quality of synthetic rubbers. It is also a raw material for making adhesives, water-based PSA, pigment and chewing gum.