Rosin chemical composition

The resin acids found in rosins are generally of the abietic- and pimaric-type. Rosins of various pine species differ in their content of abietic vs. pimaric-type acids. Rosins from species exhibiting high abietic-type acid compositions are preferred for production of rosin derivatives. However, the differences in properties of rosins are often associated with their non-resin acid content instead of their chemical compositions. On the other hand, the compositions of rosins from different sources greatly differ [22]. Table 8 shows a typical distribution of resin acids in rosins obtained from gum, tall oil and wood sources. 

The phthalic alkyd class is broken down into resins which are unmodified, resins which are modified, except with rosin and rosin ester, and finally resins which are modified with rosin and rosin ester. Under each class various chemical compositions are broken out for purposes of analysis. The alkyd resins modified with rosin and rosin ester are going to be considered in the rosin ester class of materials rather than the phthalic alkyd class of materials. Figures on phthalic alkyds have been available since 1933 11), The Tariff Commission has used more than one type of breakdown over this period. In 1946 they broke down total alkyds into two classes oil-type alkyds as compared with other than oil-type alkyds. Before and after that year, this breakdown was not made. 

Colophony (rosin, pine rosin, wood rosin) is obtained from various species of pine tree. It has a complex chemical composition, of which about 90% is resin acids and the rest is corresponding esters, aldehydes and alcohols. Two main types of acids occur abietic acid with conjugated double bonds and pimaric acid with non-conjugated double bonds. Colophony is not used alone as a drying resin but is used to modify other resins, such as alkyds. Colophony is an important contact sensitizer, but the esterification of organic acids in colophony with alcohol groups in alkyd resins reduces its allergenicity. Rosin esters can be used in paints and varnishes (Mathias 1984 Fischer and Adams 1990 Sadhra et al. 1994). See the chapter on colophony in this book. 

The international market of gum resin is quite variable, affecting the trade values of turpentine and rosin. Besides international standards usually required (particular chemical composition of turpentine, and specific physical properties of rosin, [76]), the prices of gum resin exported (and its by-products) may be subject to negotiation, depending on the type of customer (end user or fractionator) and the amount of tons purchased. For instance, in 2008, the average value of turpentine exported from Brazil was US 1,023.46/t Free on Board (FOB) however, the charged prices for France (the main customer of Brazilian turpentine, Table 136.2) and Spain (which acquired 584,600 kg in 2008) were US 848.85A FOB and US 1,169.88/t FOB, respectively [131]. 

The chemical reactivities of gum, wood, and tall oil rosin are significantly different due largely to their respective compositions. Table I shows typical chromatographic analyses of the three types of rosin C12. 13). It is interesting to note that the gum rosin contains the least amount of the inert dehydroabietic acid among the three types of rosin, and as expected, it exhibits the greatest adduct potential toward a dieneophile such as maleic anhydride. 

Rosin exploitation, a part of the so-called Naval Stores Industry, is at least as old as the construction of wooden naval vessels. In recent years, rosin components have attracted a renewed attention, notably as sources of monomers for polymers synthesis. The purpose of the present chapter is to provide a general overview of the major sources and composition of rosin. It deals therefore with essential features such as the structure and chemical reactivity of its most important components, viz. the resin acids, and the synthesis of a variety of their derivatives. This chemical approach is then followed hy a detailed discussion of the relevant applications, the resin acids and their derivatives, namely in polymer synthesis and processing, paper sizing, emulsion polymerization, adhesive tack and printing inks, among others. 

Solvent drying of conifer woods with water-miscible solvents such as acetone, however, remains economically unfavorable because of solvent losses and energy requirements. A limited quantity of perfumery-grade pine needle oil can be obtained from a few Pinus species, but the needle oils from most species too closely resemble turpentines to command the premium prices that would justify the production costs. Although the rosins that could be derived from needles of many pines are essentially similar to the xylem rosins, the needle rosins from other species are of unusual composition. Such rosins could be the source of specialty fine chemicals but would not have any significant impact on rosin as a commodity material. The composition of the resin acids in pine needles may be an important characteristic in chemoteixonomic and genetic studies (18). 

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