Rosin is the major product obtained from pine resin. It remains behind as the involatile residue after distillation of the turpentine and is a brittle, transparent, glassy solid. It is insoluble in water but soluble in many organic solvents. It is graded and sold on the basis of colour, the palest shades of yellow-brown being the better quality. Quality criteria and specifications are described in. Several other physico-chemical characteristics influence the quality and these are largely dependent on the species of pine from which the rosin is obtained, i.e., they are determined more by genetic than environmental and processing factors. These aspects are discussed in more detail.
Most rosin is used in a chemically modified form rather than in the raw state in which it is obtained. It consists primarily of a mixture of abietic- and pimaric-type acids with smaller amounts of neutral compounds. This intrinsic acidity, coupled with other chemical properties, enables it to be converted to a Large number of downstream derivatives which are used in a wide range of applications. The derivatives include salts, esters and maleic anhydride adducts, and hydrogenated, disproportionated and polymerized rosins. Their most important uses are in the manufacture of adhesives, paper sizing agents, printing inks, solders and fluxes, various surface coatings, insulating materials for the electronics industry, synthetic rubber, chewing gums and soaps and detergents.
Although it is more economical to manufacture derivatives if large quantities of rosin are involved, small producers often manufacture simple derivatives for sale in the domestic market as a substitute for imported products. For example, fortified rosin sizes can be made based on the reaction of rosin with maleic anhydride. However, for the purposes of this report, no further reference is made to the technical aspects of additional processing or to the products them selves.