Terpenic resins

Terpenic resins are oligomers of some unsaturated dicyclic hydrocarbons with the formula CmHie, which are found in coniferous crude oil, the turpentine resulting from the cellulose-sulfate process, and other natural materials. The main compounds of turpentine-sulfate and of some distillation fractions of this are a- and 3-pinene (Fig. 5). 

Of two components, p-pinene is of significance for the terpenic resin (TR) synthesis (a-pinene is used to obtain camphor [101]). 

TRs are thermoplastic products, the production and marketing of which began as early as 1938. They can be considered P-pinene oligomers. Their softening temperatures range between 10 and 135°C. The latter limiting value corresponds to M = 1200 to 1500 g/mol [101], 

TRs have been of particular importance in the manufacture of adhesives from natural and synthetic rubbers. The adhesive compositions obtained with these resins have an excellent balance of adhesion, cohesion, tackiness, and strength. They provide superior adhesives for applying to backings, providing excellent pressure-sensitive adhesive tapes [102]. TRs also have applications in ink or chewing gum formulations, building engineering, and the paper and leather industries [83,103,104]. 

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Heteroatom functionalized terpene resins are also utilized in hot melt adhesive and ink appHcations. Diels-Alder reaction of terpenic dienes or trienes with acrylates, methacrylates, or other a, P-unsaturated esters of polyhydric alcohols has been shown to yield resins with superior pressure sensitive adhesive properties relative to petroleum and unmodified polyterpene resins (107). Limonene—phenol resins, produced by the BF etherate-catalyzed condensation of 1.4—2.0 moles of limonene with 1.0 mole of phenol have been shown to impart improved tack, elongation, and tensile strength to ethylene—vinyl acetate and ethylene—methyl acrylate-based hot melt adhesive systems (108). Terpene polyol ethers have been shown to be particularly effective tackifiers in pressure sensitive adhesive appHcations (109). 

Terpene resins, because of their low odor and acceptable FDA clearance, are used as tackifiers for the natural and synthetic gum bases used in chewing gum. Selected petroleum resins are also used as gum bases. 

Uses ndReactions. a-Pinene (8) is useful for synthesizing a wide variety of terpenoids. Hydration to pine oil, acid-catalyzed isomerization to camphene, thermal isomerization to ocimene and aHoocimene, and polymerization to terpene resins are some of its direct uses. Manufacture of linalool, nerol, and geraniol has become an economically important use of a-pinene. 

Uses ndReactions. Some of the principal uses for P-pinene are for manufacturing terpene resins and for thermal isomerization (pyrolysis) to myrcene. The resins are made by Lewis acid (usuaUy AlCl ) polymerization of P-pinene, either as a homopolymer or as a copolymer with other terpenes such as limonene. P-Pinene polymerizes much easier than a-pinene and the resins are usehil in pressure-sensitive adhesives, hot-melt adhesives and coatings, and elastomeric sealants. One of the first syntheses of a new fragrance chemical from turpentine sources used formaldehyde with P-pinene in a Prins reaction to produce the alcohol, Nopol (26) (59). 

Uses ndReactions. The Prins reaction of 3-carene with formaldehyde in acetic acid gives mainly 2-carene-4-methanol acetate, which when saponified produces the 2-carene-4-methanol, both of which are commercial products of modest usage (60). 3-Carene (28) also reacts with acetic anhydride with a catalyst (ZnCl2) to give 4-acetyl-2-carene (29) (61), which is also a commercial product. Although 3-carene does not polymerize to produce terpene resins, copolymerization with phenol has been successfully commercialized by DRT in France (62). 

Carene has also been isomerized over an S-alumina catalyst to a 50 50 mixture of dipentene (15) and carvestrene (30). The cmde mixture can be readily polymerized to a terpene resin or copolymerized with piperjiene (63,64). 

I.4. Polyterpene resins. Terpene resins are obtained from natural terpene monomers obtained from naval stores, paper pulp production, and citrus juice production. Terpenes are found in almost all living plants, and the turpentine oil from pine trees is the most important source. 

Hydrocarbon resins, rosin, rosin ester, coumarone indene resins, and terpene resins can be directly added to solvent-borne adhesives. For latex adhesives, resin emulsification must be produced before addition. 

From a chemical point of view, vegetable resins are a complex mixture of mono-, sesqui-, di- and triterpenes, which have, respectively, 10, 15, 20 and 30 carbon atoms per molecule. The mono- and sesquiterpenes are both present in most resins. The di- and triterpenes are rarely found together in the same resin, which means that terpenic resins can be divided into two main classes. Table 1.5 lists the botanical origin and the kind of terpenoid compounds of some natural resins. 

Table 1.5 Botanical origin and chemical composition of terpenic resins...

Since the analysis of terpenic compounds is often performed together with lipids, silylation has the advantage of being able to differentiate between carboxylic acids and naturally occurring methyl esters, which can be found for example in some terpenic resins and extracted together with lipids. 

One of the many uses of terpenic resins is as the main ingredient in paint varnishes. Such varnishes are applied on the surface of paintings to protect the paint layer and to confer gloss and saturation to colours. It is important to know the characteristics... 

Some high molecular weight substances, such as highly polymerized terpenic resins or fossil resins, cannot be directly analysed by GC/MS. In these cases online analytical pyrolysis combined with GC/MS can be used. Pyrolysis-GC/MS applications are described in Chapters 11 and 12. 

Few papers deal with the use of SPME in the characterisation of terpenic resins in archaeological or museum objects [23 26]. 

SPME/GC MS in the Characterisation of Terpenic Resins 275 10.3.3 Application to Research on Olibanum [26]... 

Terpene resins are most commonly used in adhesive production, where they confer very strong tackifying properties. The terpene resins improve the resistance of adhesives to oxidative degradation. These resins are normally produced from p-pinene and are light yellow in colour. Polymers of dipentene and limonene are also available as resins. 

CA 67, 433(1967) (A description of several nonrupturing detonating cords is given. As an example, one of them is prepd by inserting a blend of PETN 85 with equal parts mixt of butyl rubber terpene resin 15% into an elastometric polyurethane sheath. 

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